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.     

The plasma Environment of Mars

Space Science Reviews -     

Characteristics of the Martian Magnetosphere according to the Data of the Mars 3 and Phobos 2 Satellites: Comparison with MGS and MAVEN Results

Cosmic Research - On January 21, 1972, the Mars 3 satellite recorded a strong (~27 nT) regular magnetic field in the region of the spacecraft’s closest approach to the dayside of Mars. Many...     

Study of notches in the Earth’s plasmasphere based on data of the <Emphasis Type="Italic">MAGION-5</Emphasis> 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 K _p = 9-and min D _st ～ ?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.     

Martian obstacle and bow shock: origins of boundaries anisotropy

The origin of the anisotropy in the shape of the Martian obstacle and bow shock is analyzed using Mars Global Surveyor observations. The influence of MHD or ion pick-up effects on Martian obstacle position was to be small found, however, localized Martian crustal magnetization increases the thickness of the downstream planetary magnetotail by 500–1000 km in agreement with earlier Phobos 2 observations. A new analytical model is presented for Martian obstacle shape variation for different solar wind ram pressure. Elongation of the Martian BS cross-section in the direction perpendicular to IMF was confirmed while the shift of this cross section in the +Y direction of Martian interplanetary medium reference frame was discovered. The shift of BS cross section in the direction of interplanetary electric field was not revealed thus not conforming the idea that mass-loading play some role in BS control.     

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.     

Unusually Distant Bow Shock Encounters at Mars: Analysis of March 24, 1989 Event

Detailed analysis of disturbances observed on 24 March, 1989 far upstream of the usual Martian bow shock position was completed with the use of the planetary obstacle and bow shock models relevant for the period of Phobos 2 observations and for low Mach numbers, respectively. It is proven that the system of discontinuities observed in the solar wind between 18:42 and 19:36 UT was the consequence of unusually distant planetary bow shock excursions. The cause was unusually small ρV ² and M _a values in the solar wind flow.     

First results of plasma and neutral gas measurements from Vega-1/2 near comet Halley

Based on the ion, electron and neutral gas observations, performed by five of the six sensors comprising the PLASMAG-1 experiment on board VEGA-1 and -2, the following results are discussed: (1) the existence of the bow shock and its location at 1.1×10⁶ km for VEGA-1 inbound; (2) the existence of a cometopause and its location at 1.6×10⁵ km for VEGA-2 inbound; (3) the plasma dynamical processes occurring inside the cometosheath; (4) the phenomena taking place within the cometary plasma region including mass-spectroscopy of cometary ions at distances 1.5×10⁴ km; (5) the existence of keV electrons near closest approach to the nucleus; and (6) the radial dependence of the cometary neutral gas and the comparison with model calculations, yielding a mean ionization scale length of 2×10⁶ km and an overall production rate of 1.3×10³⁰ molecules s⁻¹ for VEGA-1 inbound. The results are also discussed in the context of the other, both remote and in-situ, observations, performed on board the VEGA- and GIOTTO-spacecraft.