Solar wind observations on the lunar surface with the Apollo-12 ALSEP

The Apollo-12 ALSEP solar wind spectrometer obtained data from the lunar surface starting November 20, 1969. To a first approximation, the general features of the positive ion flux depend only on the instrument's orientation and location in space relative to the Sun-Earth system. However, there are some detectable effects of the interaction of the solar wind with the local magnetic field and surface, including the deceleration of incident positive ions and the enhancement of fluctuations in the plasma. The expected asymmetry of sunset and sunrise times due to the motion of the Moon about the Sun is not observed. On one occasion, the solar wind was incident on the ALSEP site as early as 36 hr (18°) before sunrise.     

Calibration of the kinematic method of studying solar wind disturbances on the basis of a one-dimensional MHD solution and a simulation study of the heliosphere disturbances between 22 november and 6 december 1977

An empirical kinematic method developed by Hakamada and Akasofu (1982) is calibrated on the basis of a one-dimensional MHD solution. The calibrated results are used to simulate the stream-stream interaction and the background corotating structure in a simple situation and also during 22 November–6 December 1977. The solar wind disturbances caused by solar activities during this period are then introduced into the above background stream in simulating the heliospheric disturbance event which was observed by an aligned set of spacecraft at distances between 0.6 and 1.6 a.u. The observations and the simulated results are satisfactory, and a little more refinement in the simulation could reconstruct reasonably well the data by filling the data gaps in the solar wind speed, the density and the IMF magnitude.     

Results of air temperature,density and pressure measurements obtained with the aid of foil cloud sensors in the height region between 80 and 95 km

Results of neutral air density, temperature and pressure measurements obtained between November 1968 and June 1972 in the height range between 80 and 95 km over Arenosillo, Spain are given. A simple foil cloud payload, primarily designed for wind finding purposes, was used. The results obtained are compared with CIRA Standard Atmosphere data and ground based radio wave absorption measurements. An estimate of the accuracy of the method is given.     

Sources of intense geomagnetic storms over the rise of solar cycle 23

In this work we present a study of the triggers of intense geomagnetic storms since the launch of the WIND spacecraft, November 1995 until December 2001. Reviewing the signatures of solar wind flow, we looked for two different kinds of interplanetary events associated with intense geomagnetic storms: ejecta and corotating solar wind streams. We also looked for the solar origin related to both events. We provide a list of the solar–terrestrial events during the rising phase of this solar cycle. The paper includes statistical conclusions that shed light onto the paradigm of geomagnetic storms.     

Sources of intense geomagnetic storms over the rise of solar cycle 23

In this work we present a study of the triggers of intense geomagnetic storms since the launch of the WIND spacecraft, November 1995 until December 2001. Reviewing the signatures of solar wind flow, we looked for two different kinds of interplanetary events associated with intense geomagnetic storms: ejecta and corotating solar wind streams. We also looked for the solar origin related to both events. We provide a list of the solar–terrestrial events during the rising phase of this solar cycle. The paper includes statistical conclusions that shed light onto the paradigm of geomagnetic storms.     

A coronal hole and its identification as the source of a high velocity solar wind stream

X-ray images of the solar corona, taken on November 24, 1970, showed a magnetically open structure in the low corona which extended from N20W20 to the south pole. Analysis of the measured X-ray intensities shows the density scale height within the structure to be typically a factor of two less than that in the surrounding large scale magnetically closed regions. The structure is identified as a coronal hole.Since there have been several predictions that such a region should be the source of a high velocity stream in the solar wind, wind measurements for the appropriate period were traced back to the Sun by the method of instantaneous ideal spirals. A striking agreement was found between the Carrington longitude of the solar source of a recurrent high velocity solar wind stream and the position of the hole.Solar wind bulk velocity and photospheric magnetic field data from the period 1962–1970 indicate the possible extension of the result to the interpretation of long term variations in the wind pattern.     

Cosmic-Ray Decreases and Interplanetary Disturbances During the Solar Magnetic Polarity Reversal in Solar Cycle 20

Using the cosmic-ray intensity data recorded with ground-based monitors at Mt. Washington and Deep River, and with cosmic-ray telescopes on Pioneer 8 and 9 spacecraft as well as the 2-hour averages of the IMF (magnitude and direction) and the solar wind bulk speed and density at 1 AU, the cosmic-ray decreases and interplanetary disturbances, that occurred during the period of solar magnetic polarity reversal in solar cycle 20, were investigated.We observed a two-step Forbush decrease on 22–23 November 1969, and a Forbush decrease on 26 November 1969, which are respectively consistent with the model of Barnden (1973), and of Parker (1963) and Barnden (1973). Only one Forbush decrease event was observed in December 1969, a period during which there was a solar magnetic polarity reversal; the Forbush decrease was attributed to a long-lived corotating high-speed solar wind stream. This is indicative that at heliolongitudes from 43° E to 70° W of S–E radial, covered by the observations, the solar magnetic polarity reversal in solar cycle 20 was not carried by, nor related to, individual transient structures, and that the reversal most probably evolved gradually.     

Geo-effectiveness of solar wind extremes

Examples of extreme events of solar wind and their effect on geomagnetic conditions are discussed here. It is found that there are two regimes of high speed solar wind streams with a threshold of ∼ 850 km s^-1. Geomagnetic activity enhancement rate (GAER) is defined as an average increase in Ap value per unit average increase in the peak solar wind velocity (Vp) during the stream. GAER was found to be different in the two regimes of high speed streams with +ve and-ve IMF. GAER is 0.73 and 0.53 for solar wind streams with +ve and -ve IMF respectively for the extremely high speed streams (< 850 km s^-1). This indicates that streams above the threshold speed with +ve IMF are 1.4 times more effective in enhancing geomagnetic activity than those with -ve IMF. However, the high speed streams below the threshold with -ve IMF are 1.1 times more effective in enhancing geomagnetic activity than those with +ve IMF. The violent solar activity period (October–November 2003) of cycle 23 presents a very special case during which many severe and strong effects were seen in the environment of the Earth and other planets; however, the z-component of IMF (Bz) is mostly positive during this period. The most severe geomagnetic storm of this cycle occurred when Bz was positive.     

Comparative analysis of recurrent high-speed solar wind streams influence on the radiation environment of near-earth space in April–July 20101

This paper analyzes variations of flux of relativistic and subrelativistic electrons in the outer radiation belt of the Earth caused by the arrival of recurrent high-speed streams of solar wind during three consecutive solar rotations. The period from April to July 2010 is covered. During this time, an increase in fluxes of relativistic electrons was observed after they had reached a minimum in November 2009–January 2010. Two coronal holes of different polarity, geometry, and location relative to the solar equator were the source of high-speed solar wind streams. The relationship between the efficiency of acceleration of electrons of subrelativistic energies and the amplitude, duration of high-speed streams of solar wind and geomagnetic disturbances, as well as the wave activity in the range of 2–7 mHz, characterized by the ULF index, is confirmed. Significant increases of the flux of relativistic electrons in the outer radiation belt of the Earth were observed during the considered period with an hourly average speed of solar wind streams above 550 km/s and a duration of more than seven days. It is found that the spectrum of electrons in the Earth’s outer radiation belt over the considered period of time was softer during the observation of solar wind streams from the positive polarity coronal hole, even given the amplitude of the solar wind velocity higher than 550 km/s.     

Meteorological conditions at the Caucasus Observatory of the SAI MSU from the results of the 2007–2015 campaign

Based on the measurements performed from 2007 to 2015 at the summit of Mount Shatdzhatmaz adjacent to the 2.5-m telescope at the Caucasus Observatory of the SAI MSU, we have determined the statistical characteristics of basic meteorological parameters: the ambient air temperature, the ground wind speed, and the relative humidity. The stability of these parameters over the entire period of our measurements and their variations within an annual cycle have been studied. The median temperature on clear nights is +3.2°C, although there are nights with a temperature below ?15°C. The typical ground wind speed is 3 m s^?1; the probability of a wind stronger than 10 m s^?1 does not exceed 2%. The losses of observing time due to high humidity are maximal in the summer period but, on the whole, are small over a year, less than 10%. We have estimated the absolute water vapor content in the atmosphere, which is especially important for infrared observations. Minimum precipitablewater vapor is observed in December–February; the median value over these months is 5 mm. We additionally provide the wind speeds at various altitudes above the ground (from 1 to 16 km) that we obtained when measuring the optical turbulence. We present the results and technique of our measurements of the annual amount of clear night astronomical time, which is, on average, 1320 h, i.e., 45% of the possible one at the latitude of the observatory. The period from mid-September to mid-March accounts for about 70% of the clear time. A maximum of clear skies is observed in November, when its fraction reaches 60% of the possible astronomical night time.     

Cosmic-Ray Variations During the Two Greatest Bursts of Solar Activity in the 23rd Solar Cycle

During two extreme bursts of solar activity in March–April 2001 and October–November 2003, the ground-based neutron monitor network recorded a series of outstanding events distinguished by their magnitude and unusual peculiarities. The important changes that lead to increased activity initiated not with the sunspot appearance, but with the large-scale solar magnetic field reconfiguration. A series of strong and moderate magnetic storms and powerful proton events (including ground-level enhancements, GLE) were registered during these periods. The largest and most productive in the 23rd solar cycle, active region 486, generated a significant series of solar flares among which the 4 November 2003 flare (X28/3B) was the most powerful X-ray solar event ever observed. The fastest arrival of the interplanetary disturbance from the Sun (after August 1972) and the highest solar wind velocity and IMF intensity were recorded during these events. Within 1 week, three GLEs of solar cosmic rays were registered by the neutron monitor network (28 and 29 October and 2 November 2003). In this work, we perform a tentative analysis of a number of the effects seen in cosmic rays during these two periods, using the neutron monitor network and other relevant data.     

CME Propagation Characteristics from Radio Observations

We explore the relationship among three coronal mass ejections (CMEs), observed on 28 October 2003, 7 November 2004, and 20 January 2005, the type II burst-associated shock waves in the corona and solar wind, as well as the arrival of their related shock waves and magnetic clouds at 1 AU. Using six different coronal/interplanetary density models, we calculate the speeds of shocks from the frequency drifts observed in metric and decametric radio wave data. We compare these speeds with the velocity of the CMEs as observed in the plane-of-the-sky white-light observations and calculated with a cone model for the 7 November 2004 event. We then follow the propagation of the ejecta using Interplanetary Scintillation measurements, which were available for the 7 November 2004 and 20 January 2005 events. Finally, we calculate the travel time of the interplanetary shocks between the Sun and Earth and discuss the velocities obtained from the different data. This study highlights the difficulties in making velocity estimates that cover the full CME propagation time.     

Site testing at Muztagh-ata site Ⅱ:seeing statistics

In this article,we present a detailed analysis of the statistical properties of seeing for the Muztaghata site which is a candidate site for hosting the future Chinese Large Optical/infrared Telescope(LOT)project.The measurements were obtained with differential image motion monitors(DIMMs) from April2017 to November 2018 at different heights during different periods.The median seeings at 11 m and6 m are very close but significantly different from that on the ground.We mainly analyzed the seeing at11 m monthly and hourly,having found that the best season for observing was from late autumn to early winter and seeing tended to improve during the night only in autumn.The analysis of the dependence on temperature inversion,wind speed and direction also was made and the best meteorological conditions for seeing are given.     

Coronal holes

Coronal holes are extensive regions of extremely low density in the solar corona within 60° of latitude from the equator. (They are not to be confused with the well-known coronal cavities which surround quiescent prominences beneath helmet streamers.) We have superposed maps of the calculated current-free (potential) coronal magnetic field with maps of the coronal electron density for the period of November 1966, and find that coronal holes are generally characterized by weak and diverging magnetic field lines. The chromosphere underlying the holes is extremely quiet, being free of weak plages and filaments. The existence of coronal holes clearly has important implications for the energy balance in the transition region and the solar wind.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

昭通大山包天文气象条件统计分析

采用云南省昭通市昭阳区气象局1960年到1988年间在大山包实地采集的气象数据资料,并根据优良太阳观测台址所要求的各项参数指标,对大山包29年来的气象资料进行了系统的统计分析,发现该候选址点在干季(10月到次年4月)具有年日照时间增长、云量减少、相对湿度降低、风速较小且风向稳定、气候变化具有明显的周期性等特征。考虑到交通条件便利,初步判定它是一个具有潜力的优良太阳观测候选址点。     

A means for improving telescope derives

In seeking to minimize local seeing, some large telescopes are being planned with less wind protection than has been traditional and some sites with very good seeing appear to suffer significantly from ground-transmitted vibration. A great care is needed in designing new telescopes to ensure that vibration does not become a dominant cause of image degradation. A supplementary drive system is proposed which could improve on past tracking performances even in such adverse conditions. The system may also reduce the costs of very large telescopes by easing the demands on the stiffness and accuracy of their mountings and drives.Paper presented at the Symposium on JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.     

Multi-Spacecraft Observations: Stream Interactions and Associated Structures

The stream interaction region (SIR), formed when a fast stream overtakes a preceding slow stream, is the predominant large-scale solar wind structure at this early phase of the STEREO mission. Using multi-spacecraft observations from STEREO A and B, ACE, Wind, and Ulysses in 2007, we analyze three stream interaction events in depth in May, August, and November of 2007, respectively, when the spacecraft had quite different spatial separations. We attempt to determine the causes of the differences in the SIR properties, whether they are spatial or temporal variations, and also to examine the steepening or widening of the SIR during its radial evolution. The presence and characteristics of associated shocks, the relation to the heliospheric current sheet, and other structures are also studied.     

Cluster Observations of the Magnetospheric Low-Latitude Boundary Layer and Cusp during Extreme Solar Wind and Interplanetary Magnetic Field Conditions: II. 7 November 2004 ICME and Statistical Survey

We present a study of the plasma properties inside and dynamics of the low-latitude boundary layer (LLBL)/cusp during the ICME event on 7 November 2004 based on data from the four Cluster spacecraft. The interplanetary magnetic field (IMF) is predominantly strongly northward, up to 50 nT, with some short-duration rotations. The observed LLBL/cusp is very thick (∼6 – 7° invariant latitude (ILAT)) and migrates equatorward with rates of 0.55° and 0.04° ILAT per minute during quick southward IMF rotations and stable northward IMF, respectively. The LLBL/cusp observed by Cluster 1 and Cluster 4 is in a fast transition between different states and is populated by different types of plasma injection, presumably coming from multiple reconnection sites. During a period of extremely northward IMF, signatures of pulsed dual reconnection inside the LLBL/cusp are observed by Cluster 3, suggesting that at least part of the LLBL/cusp is on closed field lines. However, analysis of the ion data implies that the boundary layer is formed in the dawn sector of the magnetosphere and does not slowly convect from the dayside as has been suggested previously. A statistical study of the location of the LLBL/cusp equatorward boundary during the ICME events on 28 – 29 October 2003 and 7 – 10 November 2004 is performed. During extreme conditions the LLBL/cusp position is offset by −7° ILAT from the location under normal conditions, which might be explained by the influence of the high solar wind dynamic pressure. The LLBL/cusp moves equatorward with increasing southward and northward IMF. However, the LLBL/cusp position under strong southward IMF is more poleward than expected from previous studies, which could indicate some saturation in the dayside reconnection process or enhancement of the nightside reconnection rate. The LLBL/cusp position under strong northward IMF is extremely low and does not agree with the location predicted in previous studies. For the events with solar wind dynamic pressure >10 nPa, the LLBL/cusp position does not depend on the solar wind dynamic pressure. This might indicate some saturation in the mechanism of how the LLBL/cusp location depends on the solar wind dynamic pressure.     

MACS for Global measurement of the Solar wind velocity and the Thermal electron temperature during the Total solar eclipse on 11 August 1999

MACS for Multi-Aperture Coronal Spectrometer is a fiber-optic-based spectrograph designed and used to perform global measurement of the solar wind velocity and the thermal electron temperature of the solar corona during the total solar eclipse on 11 August 1999. The motivation for the construction of MACS was provided by the theory formulated by Cram (1976) for the formation of the K-coronal spectrum and a method for determining the radial profile of the thermal electron temperature of the solar corona. Based on this theory a subsequent application was carried out by Ichimoto et al. (1996) using a slit-based spectroscopic study during the total solar eclipse on 3 November 1994. We have modified Cram's theory to incorporate the role of the solar wind velocity in the formation of the K-corona and have identified wind and temperature sensitive intensity ratios. Instead of a slit-based spectrograph MACS consists of twenty fiber optic tips placed at the focal plane of the telescope and positioned to see different radii and latitudes of the solar corona. Another fiber is placed at the center of the frame and uses the lunar shadow for a measure of the background signal. The other ends of the fibers are vertically aligned and placed at the primary focus of the collimating lens of the spectrograph thus providing simultaneous spectra from all of the fibers. In this first paper (Paper I) we describe our instrument and the obtained coronal spectra. The final and complete results will be presented in Paper II (Reginald and Davila, 2000).     

Ion escape from Mars as a function of solar wind conditions: A statistical study

The influence of solar EUV and solar wind conditions on ion escape at Mars is investigated using ion data from the Aspera-3 instrument on Mars Express, combined with solar wind proxy data obtained from the Mars Global Surveyor (MGS) spacecraft. A solar EUV flux proxy based on data from the Earth position, scaled and shifted in time for Mars, is used to study relatively long time scale changes related to solar EUV variability. Data from May 2004 until November 2005 has been used. A clear dependence on the strength of the subsolar magnetic field as inferred from MGS measurements is seen in the ion data. The region of significant heavy ion flows is compressed and the heavy ion flux density is higher for high subsolar magnetic field strength. Because of the difference in outflow area, the difference in estimated total outflow is somewhat less than the difference in average flux density. We confirm previous findings that escaping planetary ions are mainly seen in the hemisphere into which the solar wind electric field is pointed. The effect is more pronounced for the high subsolar magnetic field case.The average ion motion has a consistent bias towards the direction of the solar wind electric field, but the main motion is in the antisunward direction. The antisunward flow velocity increases with tailward distance, reaching above at 2 to 3 martian radii downtail from Mars for O⁺ ions. Different ion species reach approximately the same bulk flow energy. We did not find any clear correlation between the solar EUV flux and the ion escape distribution or rate, probably because the variation of the solar EUV flux over our study interval was too small. The results indicate that the solar wind and its magnetic field directly interacts with the ionosphere of Mars, removing more ions for high subsolar magnetic field strength. The interaction region and the tail heavy ion flow region are not perfectly shielded from the solar wind electric field, which accelerates particles over relatively large tail distances.