M. Verigin

Wind observations of the terrestrial bow shock: 3-D shape and motion

Between late 1994 and early 2001 the Wind orbiter, generally targeted to stay in the solar wind, passed through the Earth’s magnetosphere ∼50 times. About 450 distinct bow shock crossings were collected during the inbound and outbound bracketing each Wind perigee. These crossings and corresponding vectorial upstream solar wind measurements by the Wind MFI and SWE instruments are used to study the 3-D shape of the bow shock and its motion. Mapping of bow shock crossings to the Sun-Earth line and to the terminator plane is realized using a recent analytical model of the planetary bow shock. The asymmetry of the terrestrial bow shock in the terminator plane is studied as a function of Friedrichs diagram anisotropy. Analysis of the subsolar bow shock position as a function of Alfvenic Mach number Ma during intervals of magnetic field aligned solar wind flow shows that the shock tends to approach the Earth when Ma is decreasing, while for non field-aligned flows bow shock moves from the planet.

Turbulent fluctuations of plasma and magnetic field parameters in the magnetosheath and the low-latitude boundary layer formation: Multisatellite observations on March 2, 1996

The results of simultaneous analysis of plasma and magnetic field characteristics measured on the INTERBALL/Tail Probe, WIND and Geotail satellites on March 2, 1996, are presented. During these observations the INTERBALL/Tail Probe crossed the low-latitude boundary layer, and the WIND and Geotail satellites measured the solar wind’s and magnetosheath’s parameters, respectively. The plasma and magnetic field characteristics in these regions have been compared. The data of the Corall, Electron, and MIF instruments on the INTERBALL/Tail Probe satellite are analyzed. Fluctuations of the magnetic field components and plasma velocity in the solar wind and magnetosheath, measured onboard the WIND and Geotail satellites, are compared. The causes resulting in appearance of plasma jet flows in the low-latitude boundary layer are analyzed. The amplitude of magnetic field fluctuations in the magnetosheath for a studied magnetosphere boundary crossing is shown to exceed the magnetic field value below the magnetopause near the cusp. The possibility of local violation of pressure balance on the magnetopause is discussed, as well as penetration of magnetosheath plasma into the magnetosphere, as a result of magnetic field and plasma flux fluctuations in the magnetosheath.

Dynamics of the plasmasphere and plasmapause under the action of geomagnetic storms

Number density and temperature of cold H+ ion fluxes in the plasmasphere measured by the Auroral probe/Alpha 3 experiment during two geomagnetic storms are analyzed. It was found that after the onset of geomagnetic storms the plasmapause both on the night and day sides starts moving toward the Earth almost simultaneously. The delay of the beginning of plasmapause movement on the day side relative to the night side is at least much less than the corotation time of magnetic tube with cold plasma from the night sector into the day sector of the plasmasphere. It was found that the number density of cold plasma inside the daytime plasmasphere could significantly change, either decrease or increase, during moderate geomagnetic storms. Now we cannot definitely determine the reason for these variations, but we assume they are caused by variations of parameters (e.g., nmaxF2,hmaxF2) in the underlying ionosphere initiated by geomagnetic storms.

Heavy ions in the magnetosphere of Mars: Phobos 2/TAUS observations

Abstract Data on heavy ion (mass/charge ratio m i q > 3 ) fluxes in the Martian plasma sheet collected by the TAUS experiment aboard the Phobos 2 orbiter and data of the MAGMA magnetometer are analyzed statistically. The analysis suggests that acceleration due to magnetic field line stresses and acceleration in the central current sheet could account for the observations, though planetary ions are likely to be preaccelerated to velocities of 40 – 50 km/s. The effectiveness of these acceleration processes of heavy ions in cases of high and low solar wind ram pressure is considered.

Study of notches in the Earth’s plasmasphere based on data of the MAGION-5 satellite

Depleted narrow (localized in longitude) regions (field tubes) in the plasmasphere, recently discovered in He+ radiation measurements on the IMAGE spacecraft, were first directly observed by the Magion-5 satellite. The low-density regions (notches) occupy <∼ 10–30° in longitude and extend from L ∼ 2–3 to the plasmasphere boundary in neighboring plasmasphere regions with larger densities. The Magion-5 data give evidence that in the low-density regions temperature is enhanced as compared to the neighboring denser plasmasphere regions. Formation of notches in the plasmasphere is, apparently, associated with AE intensification during weak magnetic storms, while strong magnetic storms usually result in the overall reduction of plasmasphere dimensions. However, even a strong magnetic storm on April 6–7, 2000 (max Kp = 9-and min Dst ∼ −290 nT), but accompanied by an isolated AE impulse, resulted in a density decrease only in the longitudinally limited post-midnight sector of the plasmasphere.

On the possibility of identifying heavy ion acceleration processes in the magnetotail of Mars

The dependence of the energy of ions on their mass could be a useful tool for the identification of possible acceleration processes in the Martian plasma sheet. The study is based on a few cases when heavier ions and protons were registered simultaneously in the plasma sheet by the TAUS energy spectrometer, and on published data of the ASPERA instrument. The analysis of mass dependence of the ion energy in the plasma sheet suggests that frictional preacceleration of ions probably in the pole regions of the Martian magnetosphere can be responsible for not more than 40% of the energy gain of heavy ions in the plasma sheet, the cross-tail current sheet acceleration yields up to 70%, and from 30 to 70% of the heavy ion energy is provided by the acceleration due to magnetic field line stresses (and/or electric field aligned acceleration).

Plasmapause dynamics during magnetic storms as observed by the Auroral Probe/Alpha 3 experiment

Abstract Some examples of distributions n ( L ), T i ( L ), and T e ( L ) measured in the outer plasmasphere during geomagnetically quiet and disturbed periods aboard Auroral Probe of the INTERBALL mission are presented. Dependencies of the plasmapause position on time for different geomagnetic activity levels are considered. Data on plasmapause dynamics during magnetic storms were also obtained. It turned out that in all considered cases the plasmapause started to move towards the Earth before the main phase of the magnetic storm and possibly just after sudden commencement. In some cases during magnetically quiet periods plasmapause may be asymmetric in noon-midnight direction. Asymmetry value may reach 1.3L0.

Thermal structure of dayside plasmasphere according to the data of Tail and Auroral Probes, and Magion-5 satellite

We consider the results of measurements of density and temperature of cold plasma in the dayside sector of the plasmasphere. The measurements were made by Interball-1 (Tail Probe) in November 1995, by Interball-2 (Auroral Probe) in August 1996 (the periods close to the solar cycle minimum), and by the Magion-5 satellite in June 2000 (this period is close to the solar cycle maximum). It was shown by the measurements in the dayside sector of the plasmasphere that, contrary to expectations of model distributions of temperature in the plasmasphere [1, 2], under quiet geomagnetic conditions the temperature of hydrogen ions of the cold plasma filling the plasmasphere was observed to increase at altitudes 5000 km < H < 10000 km. Its altitude gradient was equal to ∼0.5 deg/km, the geomagnetic latitude being variable within the limits 10° < λ < 40°. The maximum values of temperature of protons, as measured by Tail Probe and Auroral Probe deep in the plasma-sphere, were equal to ∼4000–6000 K. According to the data obtained by the Magion-5 satellite in the depth of the plasmasphere, these temperatures varied within the limits 7500–8500 K. These results can be considered as some indication of a dependence of the plasmasphere thermal structure on the phase of the solar cycle. In the region 2.5 < L < 5 and at geomagnetic latitudes λ < 40°, drops of the ion temperature were regularly observed with values reaching ∼2000 K.

Konstantin Gringauz 1918–1993: Approach to scientific biography

Abstract The paper briefly presents scientific accomplishments of Professor K.I. Gringauz, who was a pioneer of in-situ space plasma studies and discovered the Earths plasmasphere and the solar wind.

GAS 2 instrument for neutral solar wind detectinga

Abstract The GAS 2 instrument is designed to detect neutral atoms (especially H) of the solar wind with typical energies of about 1 keV. To separate fast atoms from intense flux of photons from the sun the coincidence technique was used. The instrument was tested and calibrated and it was shown that GAS 2 could really measure various kinds of light neutral atoms and ions in keV energy range in the presence of ultraviolet radiation.