Evolution of Cosmic-Ray Intensities While the Earth Was Engulfed by the Interplanetary Storm (Blob) of 1 – 3 October 2013

When a Coronal Mass Ejection (CME) is ejected by the Sun, it reaches the Earth orbit in a modified state and is called an ICME (Interplanetary CME). When an ICME blob engulfs the Earth, short-scale cosmic-ray (CR) storms (Forbush decreases, FDs) occur, sometimes accompanied by geomagnetic Dst storms, if the B _z component in the blob is negative. Generally, this is a sudden process that causes abrupt changes. However, sometimes before this abrupt change (FD) due to strong ICME blobs, there are slow, small changes in interplanetary parameters such as steady increases in solar wind speed V, which are small, but can last for several hours. In the present communication, CR changes in such an event are illustrated in the period 1?–?3 October 2013, when V increased steadily from ～?200 km?s^?1 to ～?400 km?s^?1 during 24 hours on 1 October 2013. The CR intensities decreased by 1?–?2 % during some hours of this 24-hour interval, indicating that CR intensities do respond to these weak but long-lasting increases in interplanetary solar wind speed.     

Nonlinear Dynamics of Ionization Fronts in HII Regions

Hydrodynamic instability of an accelerating ionization front (IF) is investigated with 2D hydrodynamic simulations, including absorption of incident photoionizing photons, recombination in the HII region, and radiative molecular cooling. When the amplitude of the perturbation is large enough, nonlinear dynamics of the IF triggered by the separation of the IF from the cloud surface is observed. This causes the second harmonic of the imposed perturbation to appear on the cloud surfaces, whereas the perturbation in density of ablated gas in the HII region remains largely single mode. This mismatch of modes between the IF and the density perturbation in the HII region prevents the strong stabilization effect seen in the linear regime. Large growth of the perturbation caused by Rayleigh-Taylor-like instability is observed late in time.     

A Detailed Comparison of Cosmic Ray Gaps with solar Gnevyshev Gaps

After increasing almost monotonically from sunspot minimum, sunspot activity near maximum falters and remains in a narrow grove for several tens of months. During the 2–3 years of turmoil near sunspot maximum, sunspots depict several peaks (Gnevyshev peaks). The spaces between successive peaks are termed as Gnevyshev Gaps (GG). An examination showed that the depths of the troughs varied considerably from one GG to the next in the same cycle, with magnitudes varying in a wide range (<1% to ∼20%). In any cycle, the sunspot patterns were dissimilar to those of other solar parameters, qualitatively as well as quantitatively, indicating a general turbulence, affecting different solar parameters differently. The solar polar magnetic field reversal does not occur at the beginning of the general turmoil; it occurs much later. For cosmic ray (CR) modulation which occurs deep in the heliosphere, one would have thought that the solar open magnetic field flux would play a crucial role, but observations show that the sunspot GGs are not reflected well in the solar open magnetic flux, where sometimes only one peak occurred (hence no GG at all), not matching with any sunspot peak and with different peaks in the northern and southern hemispheres (north – south asymmetry). Gaps are seen in interplanetary parameters but these do not match exactly with sunspot GGs. For CR data available only for five cycles (19 – 23), there are CR gaps in some cycles, but the CR gaps do not match perfectly with gaps in the solar open magnetic field flux or in interplanetary parameters or with sunspot GGs. Durations are different and/or there are variable delays, and magnitudes of the sunspot GGs and CR gaps are not proportional. Solar polar magnetic field reversal intervals do not coincide with either sunspot GGs or CR gaps, and some CR gaps start before magnetic field reversals, which should not happen if the magnetic field reversals are the cause of the CR gaps.     

A Preliminary Estimate of the Size of the Coming Solar Cycle 24, based on Ohl’s Precursor Method

For many purposes (e.g., satellite drag, operation of power grids on Earth, and satellite communication systems), predictions of the strength of a solar cycle are needed. Predictions are made by using different methods, depending upon the characteristics of sunspot cycles. However, the method most successful seems to be the precursor method by Ohl and his group, in which the geomagnetic activity in the declining phase of a sunspot cycle is found to be well correlated with the sunspot maximum of the next cycle. In the present communication, the method is illustrated by plotting the 12-month running means aa(min ) of the geomagnetic disturbance index aa near sunspot minimum versus the 12-month running means of the sunspot number Rz near sunspot maximum [aa(min ) versus Rz(max )], using data for sunspot cycles 9 – 18 to predict the Rz(max ) of cycle 19, using data for cycles 9 – 19 to predict Rz(max ) of cycle 20, and so on, and finally using data for cycles 9 – 23 to predict Rz(max ) of cycle 24, which is expected to occur in 2011 – 2012. The correlations were good (∼+0.90) and our preliminary predicted Rz(max ) for cycle 24 is 142±24, though this can be regarded as an upper limit, since there are indications that solar minimum may occur as late as March 2008. (Some workers have reported that the aa values before 1957 would have an error of 3 nT; if true, the revised estimate would be 124±26.) This result of the precursor method is compared with several other predictions of cycle 24, which are in a very wide range (50 – 200), so that whatever may be the final observed value, some method or other will be discredited, as happened in the case of cycle 23.     

Serendipitous Asteroid Lightcurve Survey Using SuperWASP

The SuperWASP project is an ultra-wide angle search for extra solar planetary transits. However, it can also serendipitously detect solar system objects, such as asteroids and comets. Each SuperWASP instrument consists of up to eight cameras, combined with high-quality peltier-cooled CCDs, which photometrically survey large numbers of stars in the magnitude range 7–15. Each camera covers a 7.8 × 7.8 degree field of view. Located on La Palma, the SuperWASP-I instrument has been observing the Northern Hemisphere with five cameras since its inauguration in April 2004.The ultra-wide angle field of view gives SuperWASP the possibility of discovering new fast moving (near to Earth) asteroids that could have been missed by other instruments. However, it provides an excellent opportunity to produce a magnitude-limited lightcurve survey of known main belt asteroids. As slow moving asteroids stay within a single SuperWASP field for several weeks, and may be seen in many fields, a survey of all objects brighter than magnitude 15 is possible. This will provide a significant increase in the total number of lightcurves available for statistical studies without the inherent bias against longer periods present in the current data sets.We present the methodology used in the automated collection of asteroid data from SuperWASP and some of the first examples of lightcurves from numbered asteroids.     

The impact of correlated noise on SuperWASP detection rates for transiting extrasolar planets

The evolution of the Alfvén turbulence due to three-wave interactions is discussed using kinetic theory for a collisionless, thermal plasma. There are three low-frequency modes, analogous to the three modes of compressible magnetohydrodynamics (MHD). When only Alfvén waves are considered, the known anisotropy of turbulence in incompressible MHD theory is reproduced. Inclusion of a fast mode wave leads to the separation of turbulence into two regimes: small wave numbers where three-wave processes involving a fast mode are dominant, and large wave numbers where the three Alfvén wave process is dominant. Possible application of the anisotropic Alfvén turbulence to the interstellar medium and dissipation of magnetic energy in magnetars are discussed.     

Variability in the Periodicity of 27 Days in Solar Indices

The short-term variation of solar indices, though typically near the solar rotation period of 27 days, can often deviate considerably from 27 days, in a wide range ∼ 19–33 days. The peak locations are within a day or two for all solar indices, indicating that the whole of the solar atmosphere is affected in a similar way. There are no systematic differences between the peaks of the chromosphere and the corona as such, but F10, X-rays, and coronal green line, which have uncertainties about their solar altitudes of origin, do show some differences (earlier peaks) as compared to other indices (chromospheric as well as coronal).     

Long-Term and Medium-Term Variations of Solar Radio Emissions at Different frequencies

Plots of 12-month moving averages of the radio emission values for 1947–2002 indicated that the ratios (maximum/minimum) of the solar cycles 19–23 were low (∼ 1.2) in the upper chromosphere and lower corona (frequencies near 15 000 MHz), rose to maximum levels of ∼ 3.5 in the middle corona (frequencies ∼ 2000±500 MHz), and dropped thereafter to ∼ 2.5. In some cycles, there were two maxima separated by about 2 years. In cycles 20 and 23, mostly the second maximum was larger than the first maximum, but in cycles 21 and 22, some parameters showed the first maximum larger while others showed the second maximum larger. There was no systematic shift from first maximum to second maximum, with frequency or temperature (or altitude).