Effects of the IMF pro- and anti-sectors in the winter midlatitude ionosphere

Summary On the basis of the 1966–73 data, the effect of the difference between pro- and anti-sectors of the IMF is found to be negligible in the winter midlatitude (Central Europe) ionosphere contrary to the dominant effect of this difference in the high-latitude ionosphere found earlier.

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a ¶rt;a a 1966–73. u¶rt;m u m amu ¶rt; pro- u anti- mau . na a u ¶rt;um (¶rt; na) u, , a naa a, naum um u.

     

The IMF structure effects in vernal and autumnal midlatitude ionosphere

au a u naam u a nu¶rt; 1963–1973 . naam, m aum mun ma m mm nam aum n (II) na¶rt;am m u a uu ¶rt; u u,¶rt; ua ma u¶rt;, u u¶rt;a ma mn muna. mu u m ¶rt;u mam nm nmum n¶rt;auma amu m m mm II u a¶rt; ¶rt; n.     

Influence of the IMF sector boundaries on cosmic rays and tropospheric vorticity

Summary The effect of the IMF sector boundary crossing (IMF SBC) in the vorticity area index (VAI) — the well-known dip in the VAI after IMF SBC — is found to be independent of the IMF SBC effect in the cosmic ray flux. This finding refutes a recent suggestion by Lundstedt [1] that the IMF SBC effect in VAI is caused by a decrease in cosmic ray flux, but supports the concept of the IMF SBC effects in the ionosphere and atmosphere developed by Latovika [2–4]. Cosmic rays seem to affect the troposphere in another way.

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¶rt;mu nu mau nam aum n ( ) a u¶rt; na¶rt;u aumu () — um uu n — a¶rt; auu m ma nm uu . mm mam nam ¶rt;a n¶rt;u ¶rt;m¶rt;a [1], m m a nuu nma uu , n¶rt;¶rt;uam nu m u u am, aum amu [2–4]. am m uu u m um a mn ¶rt;u a.

     

Effects of the imf sector structure in the midlatitude troposphere and stratosphere

Summary The data on geopotential heights and temperatures at 7 pressure levels between 1000-10 hPa above Berlin(52.5 °N, 13.4 °E) are analysed for the winters of 1963–1973. No demonstrable effect of the interplanetary magnetic field sector boundary crossing (IMF SBC) is found in the lower and middle stratosphere, but there is a demonstrable effect in the middle troposphere at the 500 hPa level. This effect is less important than the IMF SBC effect in the tropospheric vorticity area index and seems to be of a different type.

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auum ¶rt;a nnmua m u mnam a 7 nm ¶rt;au ¶rt; 1000-10 a a¶rt; u(52,5 °.., 13,4 °.¶rt;.) ¶rt; u 1963–1973. ua ¶rt;aam m nu mau nam aum n( ) ¶rt;a amu u u ¶rt; mam, ma m a¶rt; ¶rt; mn a 500 a. mm m a, m u¶rt; na¶rt;u aumu am, u am m ¶rt; muna.

     

Dusty plasma in the midlatitude ionosphere during meteor showers

The emission (or modulation) line, which manifests itself during high-speed (the speed of entry into the atmosphere is about 70 km/s) meteor showers (Perseids, Orionids, Leonids), has been detected in the fluctuation spectra of ionospheric plasma radio noise at λ = 2 m. The line frequency varies from 12 to 60 Hz depending on activity of ionospheric ionization sources and local characteristics of a meteor shower, time of day, etc. The line has a width of 2–3 Hz and can have satellites. The dusty plasma characteristics have been estimated on the assumption that ionospheric noise is modulated or emitted due to dusty plasma oscillations.     

Effects of the interplanetary magnetic field sector structure in the winter ionosphere

Summary The ionospheric effects of the interplanetary magnetic field (IMF) sector boundary crossings are studied for the winters of 1963–69. They are considerably stronger for proton than for non-proton sector boundaries. There are two different types of effects. The geomagnetic type is a disturbance, observed in geomagnetic activity, the night-time ionosphere and the day-time F2 region near the geomagnetic equator. The effect in the ionosphere is interpreted in terms of the IMF sector boundary crossing related changes in geomagnetic activity. The tropospheric type is aquietening, observed in tropospheric vorticity and in the day-time mid-and low-latitude ionosphere (except the geomagnetic equator region). The mechanism of this effect remains unexplained.

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¶rt;m u m nu mau nam aum n () ¶rt; u 1963–69. u m u ¶rt; nm ¶rt; a mau. mm ¶rt;a m¶rt; muna m. aum m u, a¶rt;a aum amumu, u u ¶rt; F2 amu uuaum ama. mu u m ¶rt;mu uu aum amumu, m a nu mau . n mun m nu, a¶rt; aumu mn u ¶rt; ¶rt;- u uum u (a uu amuaum ama). au m ma um.

     

The response of the high-latitude ionosphere to IMF variations

The convection of plasma in the high-latitude ionosphere is strongly affected by the interplanetary magnetic field (IMF) carried by the solar wind. From numerous statistical studies, it is known that the plasma circulation conforms to patterns that are characteristic of particular IMF states. Following a change in the IMF, the convection responds by reconfiguring into a pattern that is more consistent with the new IMF. Some early studies reported that the convection first begins to change near noon while on the dawn and dusk flanks and on the nightside it remains relatively unaffected for tens of minutes. Work by Ridley et al. (J. Geophys. Res. 103 (1998) 4023–4039) and Ruohoniemi and Greenwald (Geophys. Res. Lett. 25 (1998) 2913–2916) that was based on measurements with more global sets of instruments challenged this view. A debate ensued as to the true nature of the convection response. We follow the arguments of Lockwood and Cowley (J. Geophys. Res. 104 (1999) 4387–4391) and Ridley et al. (J. Geophys. Res. 104 (1999) 4393–4396) by reviewing recent results on the timing of the onset of the convection response to the changed IMF. We discuss the timing problem from the perspectives of observations and modeling. In our view, the onset of the ionospheric response to changed IMF is globally simultaneous on time scales of a few minutes. A physical basis for the rapid communication of effects in the dayside convection to the nightside has been demonstrated in magnetohydrodynamic simulations. We also offer some cautionary notes on the timing of convection changes and the use of global assimilative techniques to study local behavior.     

第24太阳活动周中纬度电离层低电离水平的观测研究

延续2008—2009年的太阳极低活动期,第24太阳活动周开始后太阳活动性上升缓慢,即使在趋近峰年时太阳极紫外(EUV)辐射通量的水平仍显著低于前几个活动周.比较第23、24周的太阳辐射水平,及日本国分寺和子午工程武汉站的电离层测高仪观测,发现第24周的太阳EUV辐射、电离层F区临界频率(foF2)和峰值高度(hmF2)都显著低于第23周的同期水平;在较低高度上,偏低的EUV辐射带来的电子密度变化不明显,而峰值电子密度(NmF2)和0.1~50 nm太阳EUV辐射通量在多数时候都同步的偏低25%~50%;但是在夏季NmF2与EUV辐射的关联性较差,即NmF2的偏低在夏季较少.分析认为这与热层中性风的季节特点有关:在夏季午后,吹向极区的子午向风总是较弱,在第24周偏低的EUV辐射背景下,减弱的离子曳力使其他季节的极区向风得到增强,进一步促进了NmF2和hmF2的降低,使这一机制的效果非常显著.基于上述结论,在对第24周电离层进行预测预报时,需更多地考虑非直接电离机制的影响.总体而言,第24周的热层和电离层变化特征可能将有别于之前几个活动周的观测,并偏离人们在此基础上所形成的认识.     

Multi-instrument probing of the polar ionosphere under steady northward IMF

Observations are presented of the polar ionosphere under steady, northward IMF. The measurements, made by six complementary experimental techniques, including radio tomography, all-sky and meridian scanning photometer optical imaging, incoherent and coherent scatter radars and satellite particle detection, reveal plasma parameters consistent with ionospheric signatures of lobe reconnection. The optical green-line footprint of the reconnection site is seen to lie in the sunward plasma convection of the lobe cells. Downstream in the region of softer precipitation the reverse energy dispersion of the incoming ions can be identified. A steep latitudinal density gradient at the equatorward edge of the precipitation identifies the general location of an adiaroic boundary, separating the open field lines of polar lobe cells from the closed field of viscous-driven cells. Enhancements in plasma density to the south of the gradient are interpreted as ionisation being reconfigured as it is thrust against the boundary by the antisunward flow of the viscous cells near noon. Each of the instruments individually provides valuable information on certain aspects of the ionosphere, but the paper demonstrates that taken together the different experiments complement each other to give a consistent and comprehensive picture of the dayside polar ionosphere.On sabbatical leave from Artic Geophysics, University Courses on Svalbard, N-9170 Longyearbyen, Norway     

Anomalous solar-diurnal variations in cosmic rays related to crossing of the IMF sector boundaries by the Earth and the problem of earthquakes

Based on a comparison of the cases of a decrease in the ratio of A _n/A _μ (where A _n and A _μ are the amplitudes of the diurnal variations of the neutron and hard cosmic ray components) to the instants of the Earth crossing the neutral IMF, it has been indicated that the process of such crossing is most effective for stimulating large destructive earthquakes with a magnitude of M ≥ 6. The 11-year period in the cyclicity of the occurrence probability of the above earthquakes has been revealed.     

Response of the nighttime midlatitude ionosphere to the passage of an atmospheric gravity wave

Using the data of the ionospheric vertical sounding in Almaty, the response of various parameters of the nighttime F layer to the passage of an atmospheric gravity wave, generated during the large magnetic storm on July 24–25, 2004, is studied. The analysis of the phase relations between the variations in the electron density at the F layer maximum (NmF), the layer maximum height (hmF), and the layer half-thickness showed that they are determined by the slope of the wave phase front. It is shown that the half-thickness of the layer changes in anti-phase with the variations in NmF2. The known fact that the amplitudes of variations in the critical frequencies of the F ₂ layer are smaller than the amplitudes of electron density variations at fixed heights is explained.     

Stratospheric ozone variability near the IMF sector boundary

Summary We search for the effects of the interplanetary magnetic field (IMF) sector boundary crossing (SBC) in upper stratospheric ozone. The SBUV data (Nimbus-7) at the 10, 3 and 1 hPa levels are analysed for latitudes 45° N and 55° N for winters of the period December 1979 to December 1982. An effect of the IMF SBC wos only found at the 10 hPa level. These first results concerning the IMF SBC effect in upper stratospheric ozone are rather preliminary.

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¶rt;m uu nu mau () nam aum n () a mam. SBUV ¶rt;a (u-7) a nm ¶rt;au 10, 3 u 1a aauum ¶rt; um 45° u 55° . . ua nu¶rt;a ¶rt;a 1979 – ¶rt;a 1982. m uu a¶rt; m a 10a. mu n mam n uuu a mam m n¶rt;aumu.

     

Response of the midlatitude ionosphere to extreme geomagnetic storms of the 23rd solar cycle

The ionospheric response in the Irkutsk region (52.3° N, 104.3° E) to the extreme geomagnetic storms of solar cycle 23 was studied based on the data of the Irkutsk incoherent scatter radar (ISR) and DPS-4 vertical sounding digital ionosonde. The deviations of parameters from the undisturbed level, i.e., from the monthly medians or the values obtained on a quiet day, were considered as an ionospheric response. Values of the electron concentration maximum (N _mF2) and electron temperature (T _e) at a height of 350 km were chosen as parameters. The ionospheric response is interpreted in the scope of the concept of a thermospheric storm and penetration of the magnetospheric electric field.     

Changes in the reflectivity of the midlatitude ionosphere with respect to the ULF (Pc1) signal

Summary The method of numerical modelling of ionospheric filtration of the Fourier components of a signal from the frequency range of Pc1 micropulsations is employed in the spectral analysis (frequency f, angle of incidence ) of the relative characteristic of the amplitude and energy reflectivity of the ionospheric layer with respect to ordinary Alfvén modes incident in the meridional plane. The results are presented for four different models characterizing the midlatitude day- and night-time ionosphere under low and high solar activity. The results indicate the specificity of filtration of ordinary Alfvén waves. It is proved that the lower region of the modelled ionosphere, as part of the midlatitude ionospheric wave guide (in particular the F2 layer), behaves like an Alfvén resonator in the given spectral range.

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m¶rt; u ¶rt;uau u umauu -mau uaa u amm ¶rt;uanaa unau 1 n¶rtum nma aau (amma f, a¶rt;u ) mum anum¶rt; u mu maamu u ¶rt; ¶rt; a, a¶rt;au a u u¶rt;ua nmu. mam n¶rt;aam ¶rt; m a ¶rt; ¶rt;um m ¶rt; u u nu u u nu amumu. aam nuum umauu a. naa, m ua am ¶rt;ua u (a am F2-u ¶rt;um ¶rt;a) ¶rt;m nma ¶rt;uana a am a.

     

Some features of nighttime enhancements in the electron concentration in the F2-layer maximum of the midlatitude ionosphere

Using the data of vertical sounding of the ionosphere in Alma-Ata (76°55′ E, 43°15′ N) conducted in 2002–2012, the reaction of parameters of the ionospheric F2 layer to various types of nighttime enhancements in the electron concentration in the maximum of the layer (NmF2) was studied, including the height of the maximum and bottom of the layer, its semithickness, and electron concentration at some fixed heights. Examples of recordings of a combination of the enhancements caused by different mechanisms are presented. The similarity of the reaction of the F2-layer parameters to the nighttime enhancements caused by the rise of the layer and plasma flux from the protonosphere and passage of large-scale travelling ionospheric disturbances was found. Difficulties in identifying these two events in the case of their equal duration are noted. The difference in the reaction of the F2-layer parameters to the enhancements caused by the rise of the layer and plasma fluxes from the protonosphere and occurrence of the summer midlatitude ionospheric anomaly is shown.     

Ionospheric signatures of magnetospheric boundaries in the post-noon sector

Spatial structures in ionospheric electron density revealed in a tomographic image have been identified with auroral forms and related to their sources in precipitating particles observed by DMSP satellites. The observations of plasma enhancements relate to discrete auroral arcs seen in the post-noon sector, identified by both red- and green-line emissions measured by a meridional scanning photometer. The features lie within a very narrow latitudinal band on L-shells where the satellite detectors observed electron precipitation classified as from the boundary plasma sheet (BPS). The harder particles are identified with an E-region structure, while further north the precipitation is softer, resulting in a localised F-layer blob and 630.0 nm emissions. A steep gradient in plasma density represent a signature in the ionosphere of the central plasma sheet (CPS)/BPS boundary. A transition to a less-structured F-layer is found on crossing the convection reversal boundary.On leave from Artic Geophysics, University Course on Svalbard (UNIS), N-9170 Longyearbyen, Norway     

Dynamics of the plasmasphere in the dusk sector as observed in the outer ionosphere

Summary Direct measurements of the thermal plasma parameters in the topside ionosphere reveal variations of the plasmasphere boundary in the dusk sector. The ACTIVE satellite's near-polar orbits at altitudes of 500 – 1800 km around winter solstice 1989 were used to study the bulge region of the plasmasphere during intervals with different levels of geomagnetic agitation. The narrow, sharply defined trough in electron concentration corresponding to the plasmapause under quiet conditions situated at L = 6 – 7 moved to lower L-values with increasing geomagnetic activity. This narrow trough can be found in all main ion constituents. During periods of moderate geomagnetic activity, following the onset of a weak magnetic storm, a portion of the plasmaspheric bulge region was separated from the main plasmaspheric body. This can be seen in the outer ionosphere as an inner narrow trough at lower L-value. Troughs in light ions need no longer coincide with this in electron concentration. He⁺ is the most sensitive constituent reflecting the dusk sector plasmaspheric situation at this altitude.Dedicated to the Memory of Professor Karel P     

The IMF sector structure effects in total ozone in central Europe

Summary The influence of the IMF sector structure on the total ozone content is studied in the European middle latitudes (5 stations,46°–52°N, 1°W–20°E) for the winters of the period 1963–1982. The average effect of the IMF sector boundary crossing (SBC) is very weak. The correction for the seasonal trend is quite crucial. Only detrended results are considered to be reliable. A statistically significant and relatively large effect is found to exist in the total ozone only for geoactive proton sector boundaries, while there is no demonstrable effect for non-proton (common) sector boundaries. The effect of proton boundaries consists in a decrease of the total ozone from higher values before the IMF SBC to lower values after the IMF SBC and it differs from the common types of IMF SBC effects. Our results seem to explain the contradiction between results obtained by other authors.

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¶rt;m uu m mm nam aum n () a n ¶rt;au a nu ¶rt;u uma (5 mau, 46° – 52° .., 1° .¶rt;. – 20° .¶rt;.) ¶rt; u nu¶rt;a 1963–1982. ¶rt;u m nu mau () a. naa a m¶rt; ma. mam mau m¶rt;a umam ¶rt;mu. mamumuu au u a m a¶rt; n ¶rt;auu a m ¶rt;amu nm mau. a mau ua ma m. m nm mau mum na¶rt;uu n ¶rt;au a u au ¶rt; ¶rt; uu au n . a am, m au mam m nmuu ¶rt; mamau ¶rt;u am.

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Presented at the XIX General Assembly of IUGG, Vancouver 1987.     

东亚扇区中低纬地区电离层暴的统计分析

用1957~2006年间515个主相单步发展的磁暴事件,分析东亚扇区4个中低纬台站的电离层扰动类型及电离层暴开始时间,得到该地区电离层暴随纬度、季节和地方时的分布规律.研究表明,中纬区负暴明显,低纬区正暴明显;夏季负暴比正暴多,冬季正暴比负暴多,春秋季正负暴分布表现出明显的纬度差异.在东亚扇区,中纬区负暴开始时间主要分布在夜间及清晨时段,且在正午至午后时段极少发生.低纬区正暴开始时间主要发生在白天时段,且在夜间18~21 LT时段也易发生正暴.中低纬电离层正相暴平均延迟时间在10 h以内,负相暴平均延迟时间在10 h以上,且中纬区延迟时间明显比低纬区短.电离层暴延迟时间与磁暴主相开始时间对应的地方时很相关,正相暴对白天发生的磁暴比对晚上发生的磁暴响应快些,而负相暴正好相反.但电离层暴延迟时间与磁暴强度之间并没有十分明显的依赖关系.     

The coherence between the IMF and high-latitude ionospheric flows: The dayside magnetosphere–ionosphere low-pass filter

This study seeks to establish a new system characteristic describing dayside convective flows in the coupled magnetosphere–ionosphere: the low-pass filter function through which interplanetary magnetic field (IMF) fluctuations are processed as they are communicated from the magnetopause to the high-latitude ionosphere near local noon. In doing so, this study confirms that variations in the ionospheric flows at high-latitudes near local noon are well correlated with variations in the IMF orientation and magnitude on short timescales. We construct the filter function by comparing time series of the ionospheric equivalent flows at a fixed location at magnetic local noon and 80° latitude with time series of the IMF. The coherence spectra of these two parameters—averaged over 330 h of comparison—indicate that there is a low-pass cutoff in the ionospheric response to IMF driving at a periods shorter than 20 min (frequencies higher than 0.8 mHz). When there is sufficient power in the IMF fluctuations, this cutoff is relatively sharp—the coherence drops by roughly a factor of three between the periods 32 and 21 min (0.5 and 0.8 mHz). The results also show that on average the coherence between the east–west component of the equivalent flows and IMF B_y tends to be less than the coherence between the north–south component of the equivalent flows and IMF B_z.