scholarly journals A Survey of large, rapid solar wind dynamic pressure changes observed by Interball-1 and IMP 8

2002 ◽  
Vol 20 (3) ◽  
pp. 293-299 ◽  
Author(s):  
P. A. Dalin ◽  
G. N. Zastenker ◽  
K. I. Paularena ◽  
J. D. Richardson
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Solar Wind Plasma ◽  
High Time Resolution ◽  
Pressure Balance ◽  
Large Pressure ◽  
Interplanetary Physics ◽  
Statistical Survey ◽  
Pressure Changes ◽  
Short Time

Abstract. The high time-resolution solar wind ion flux measurements from Interball-1 and IMP 8 show about one hundred large, rapid dynamic the pressure changes each year. We cataloged these events by the size and transition time of the pressure changes and present a statistical survey of these events. We find that the majority of the pressure changes of more than 1–2 nPa occur over a very short time period, on the order of a few minutes or less. Most of the large pressure changes not associated with shocks are due solely to density changes with speed remaining constant. We find that pressure balance between the thermal and magnetic pressures is not maintained across most of these events, so these events are still evolving.Key words. Interplanetary physics (solar wind plasma)

Mars’ ionopause: A game of pressures

2020 ◽  
Author(s):  
Beatriz Sanchez-Cano ◽  
Clara Narvaez ◽  
Mark Lester ◽  
Michael Mendillo ◽  
Majd Mayyasi ◽  
...  
Keyword(s):  
Solar Wind ◽  
Magnetic Fields ◽  
Total Pressure ◽  
Dynamic Pressure ◽  
Solar Wind Plasma ◽  
Point Of View ◽  
Tangential Discontinuity ◽  
Pressure Balance ◽  
Thermal Pressure ◽  
Plasma Density Profile

<p>The ionopause is a tangential discontinuity in the ionospheric thermal plasma density profile that marks the upper boundary of the ionosphere for unmagnetized planets. This interface is formed by a balance of pressures, as the ionopause is the region where the total pressure of the ionosphere (ionospheric thermal pressure plus magnetic pressure) balances the solar wind ram pressure. Since only Venus and Mars have no global “dipole” magnetic fields, ionopauses are unique to those planets. For Venus, the ionopause formation is well characterized because the thermal pressure of the ionosphere is usually larger than the solar wind dynamic pressure. For Mars, however, the maximum thermal pressure of the ionosphere is usually insufficient to balance the total pressure in the overlying magnetic pileup boundary. Therefore, the Martian ionopause is not always formed, and when it does, it is located at a large range of altitudes, varies rapidly and is highly structured. In this study, we characterise the Martian ionopause formation from the point of view of the thermal, magnetic and dynamic pressure balance. The objective of this paper is to assess under which circumstances the Martian ionopause is formed, both over and far from crustal magnetic fields. We focus on three MAVEN deep dip campaigns that occurred on the dayside of Mars, and we utilize several multi-plasma and magnetic field in-situ observations from the MAVEN mission, as well as solar wind plasma observations from the Mars Express mission.</p>

scholarly journals Statistical analysis of long-duration low-density solar wind events

2001 ◽  
Vol 19 (1) ◽  
pp. 17-23 ◽  
Author(s):  
S. Watari ◽  
T. Watanabe ◽  
K. Marubashi
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Solar Wind Plasma ◽  
Occurrence Rate ◽  
In Situ Observation ◽  
Low Density ◽  
Wind Condition ◽  
Long Duration ◽  
Interplanetary Physics ◽  
Wind Events

Abstract. Low solar wind density with long duration was measured by in situ observation between 11 and 12 May 1999. As a result of this low-density solar wind condition, the magnetosphere of the Earth expanded considerably. We used a database of one-hour-averaged solar wind (1963–1999) near 1 AU to determine whether or not the observed low-density event was extremely abnormal. As a result it was found that this event has the longest duration in approximately 36 years of solar wind observations. There are three events with density 0.5 cm-3 or less and duration ten hours or longer. They were observed on 4 and 31 July 1979, and 11–12 May 1999. The 4 July 1979 event recurred on 31 July 1979. The events were characterized by low-beta, low Alfven Mach number (MA ), and low dynamic pressure. The occurrence rate of low-density solar wind with density 0.5 cm-3 or less shows several peaks near solar maxima. However, it is difficult to find a clear relationship between the sunspot number and the occurrence rate.Key words. Interplanetary physics (flare and stream dynamics; solar wind plasma; sources of the solar wind)

scholarly journals Latitudinal extent of large-scale structures in the solar wind

2003 ◽  
Vol 21 (6) ◽  
pp. 1331-1339 ◽  
Author(s):  
H. A. Elliott ◽  
D. J. McComas ◽  
P. Riley
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Spatial Scales ◽  
Coronal Holes ◽  
Solar Wind Plasma ◽  
Ecliptic Plane ◽  
Plasma Parameters ◽  
Field Polarity ◽  
Interplanetary Physics ◽  
Hydrodynamic Code

Abstract. Comparison of solar wind observations from the ACE spacecraft, in the ecliptic plane at ~ 1 AU, and the Ulysses spacecraft as it orbits over the Sun’s poles, provides valuable information about the latitudinal extent and variation of solar wind structures in the heliosphere. While qualitative comparisons can be made using average properties observed at these two locations, the comparison of specific, individual structures requires a procedure to determine if a given structure has been observed by both spacecraft. We use a 1-D hydrodynamic code to propagate ACE plasma measurements out to the distance of Ulysses and adjust for the differing longitudes of the ACE and Ulysses spacecraft. In addition to comparing the plasma parameters and their characteristic profiles, we examine suprathermal electron measurements and magnetic field polarity to help determine if the same features are encountered at both ACE and Ulysses. The He I l 1083 nm coronal hole maps are examined to understand the global structure of the Sun during the time of our heliospheric measurements. We find that the same features are frequently observed when both spacecraft are near the ecliptic plane. Stream structures derived from smaller coronal holes during the rising phase of solar cycle 23 persists over 20°–30° in heliolatitude, consistent with their spatial scales back at the Sun.Key words. Interplanetary physics (solar wind plasma)

scholarly journals Impact of solar wind depression on the dayside magnetosphere under northward interplanetary magnetic field

2011 ◽  
Vol 29 (1) ◽  
pp. 31-46 ◽  
Author(s):  
S. Baraka ◽  
L. Ben-Jaffel
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Cell Model ◽  
Dynamic Pressure ◽  
Outer Boundary ◽  
Solar Wind Plasma ◽  
Tail Region ◽  
Dayside Magnetopause

Abstract. We present a follow up study of the sensitivity of the Earth's magnetosphere to solar wind activity using a particles-in-cell model (Baraka and Ben Jaffel, 2007), but here during northward Interplanetary Magnetic Field (IMF). The formation of the magnetospheric cavity and its elongation around the planet is obtained with the classical structure of a magnetosphere with parallel lobes. An impulsive disturbance is then applied to the system by changing the bulk velocity of the solar wind to simulate a decrease in the solar wind dynamic pressure followed by its recovery. In response to the imposed drop in the solar wind velocity, a gap (abrupt depression) in the incoming solar wind plasma appears moving toward the Earth. The gap's size is a ~15 RE and is comparable to the sizes previously obtained for both Bz<0 and Bz=0. During the initial phase of the disturbance along the x-axis, the dayside magnetopause (MP) expands slower than the previous cases of IMF orientations as a result of the abrupt depression. The size of the MP expands nonlinearly due to strengthening of its outer boundary by the northward IMF. Also, during the initial 100 Δt, the MP shrank down from 13.3 RE to ~9.2 RE before it started expanding, a phenomenon that was also observed for southern IMF conditions but not during the no IMF case. As soon as they felt the solar wind depression, cusps widened at high altitude while dragged in an upright position. For the field's topology, the reconnection between magnetospheric and magnetosheath fields is clearly observed in both the northward and southward cusps areas. Also, the tail region in the northward IMF condition is more confined, in contrast to the fishtail-shape obtained in the southward IMF case. An X-point is formed in the tail at ~110 RE compared to ~103 RE and ~80 RE for Bz=0 and Bz<0, respectively. Our findings are consistent with existing reports from many space observatories (Cluster, Geotail, Themis, etc.) for which predictions are proposed to test furthermore our simulation technique.

scholarly journals Observations of interplanetary scintillation during the 1998 Whole Sun Month: a comparison between EISCAT, ORT and Nagoya data

2000 ◽  
Vol 18 (9) ◽  
pp. 1003-1008 ◽  
Author(s):  
P. J. Moran ◽  
S. Ananthakrishnan ◽  
V. Balasubramanian ◽  
A. R. Breen ◽  
A. Canals ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Wind Velocity ◽  
Solar Physics ◽  
Solar Wind Plasma ◽  
Interplanetary Scintillation ◽  
Velocity Measurements ◽  
Plasma Sources ◽  
Interplanetary Physics ◽  
Instruments And Techniques ◽  
Good Agreement

Abstract. Observations of interplanetary scintillation (IPS) allow accurate solar wind velocity measurements to be made at all heliographic latitudes and at a range of distances from the Sun. The data may be obtained with either single, double or multiple antennas, each requiring a different method of analysis. IPS data taken during the 1998 whole sun month (30th July-31st August 1998) by EISCAT, the ORT (Ooty Radio Telescope), India, and the Nagoya IPS system, Japan, allow the results of individual methods of analysis to be compared. Good agreement is found between the velocity measurements using each method, and when combined an improved understanding of the structure of the solar wind can be obtained.Key words: Interplanetary physics (solar wind plasma; sources of the solar wind) - Solar physics, astrophysics and astronomy (instruments and techniques)

The effect of solar wind dynamic pressure changes on low and mid-latitude magnetic records

1992 ◽  
Vol 19 (12) ◽  
pp. 1227-1230 ◽  
Author(s):  
C. T. Russell ◽  
M. Ginskey ◽  
S. Petrinec ◽  
G. Le
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Solar Wind Dynamic Pressure ◽  
Pressure Changes

scholarly journals Dynamical evolution of the inner heliosphere approaching solar activity maximum: interpreting Ulysses observations using a global MHD model

2003 ◽  
Vol 21 (6) ◽  
pp. 1347-1357 ◽  
Author(s):  
P. Riley ◽  
Z. Mikić ◽  
J. A. Linker
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Maximum ◽  
Dynamical Evolution ◽  
Solar Wind Plasma ◽  
Polar Regions ◽  
Activity Maximum ◽  
Interplanetary Magnetic Fields ◽  
Interplanetary Physics ◽  
Interaction Regions

Abstract. In this study we describe a series of MHD simulations covering the time period from 12 January 1999 to 19 September 2001 (Carrington Rotation 1945 to 1980). This interval coincided with: (1) the Sun’s approach toward solar maximum; and (2) Ulysses’ second descent to the southern polar regions, rapid latitude scan, and arrival into the northern polar regions. We focus on the evolution of several key parameters during this time, including the photospheric magnetic field, the computed coronal hole boundaries, the computed velocity profile near the Sun, and the plasma and magnetic field parameters at the location of Ulysses. The model results provide a global context for interpreting the often complex in situ measurements. We also present a heuristic explanation of stream dynamics to describe the morphology of interaction regions at solar maximum and contrast it with the picture that resulted from Ulysses’ first orbit, which occurred during more quiescent solar conditions. The simulation results described here are available at: http://sun.saic.com.Key words. Interplanetary physics (Interplanetary magnetic fields; solar wind plasma; sources of the solar wind)

Solar wind proton precipitation to the surface of Mercury

2020 ◽  
Author(s):  
Shahab Fatemi ◽  
Andrew R. Poppe ◽  
Stas Barabash
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Solar Wind Plasma ◽  
Solar Wind Dynamic Pressure ◽  
Solar Wind Proton ◽  
Entire Surface ◽  
The North ◽  
Proton Precipitation ◽  
Neutral Sodium ◽  
The Imf

&lt;p&gt;We examine the effects of the interplanetary magnetic field (IMF) orientation and solar wind dynamic pressure on the solar wind proton precipitation to the surface of Mercury. We use the Amitis model, a three-dimensional GPU-based hybrid model of plasma (particle ions and fluid electrons), and explain a method we found necessary to accurately calculate plasma precipitation to the surface of Mercury through the highly dynamic Hermean magnetosphere. We use our model to explain ground-based telescope observations of Mercury's neutral sodium exosphere, and compare our simulation results with MESSENGER observations. For the typical solar wind dynamic pressure near the orbit of Mercury (i.e., ~7-8 nPa) our model shows a high solar wind proton flux precipitates through the magnetospheric cusps to the high latitudes on both hemispheres on the dayside with a higher precipitation rate to the southern hemisphere compared to the north, which is associated with the northward displacement of Mercury's intrinsic magnetic dipole. We show that this two peak pattern, which is also a common feature observed for neutral sodium exosphere, is controlled by the radial component (B&lt;sub&gt;x&lt;/sub&gt;) of the IMF and not the B&lt;sub&gt;z&lt;/sub&gt; component. Our model also suggests that the southward IMF and its associated magnetic reconnection do not play a major role in controlling plasma precipitation to the surface of Mercury through the magnetospheric cusps, in agreement with MESSENGER observations that show that, unlike the Earth, there is almost no dependence between the IMF angle and magnetic reconnection rate at Mercury. For the typical solar wind dynamic pressure, our model suggests that the solar wind proton precipitation through the cusps is longitudinally centered near noon with ~11&lt;sup&gt;o&lt;/sup&gt; latitudinal extent in the north and ~21&lt;sup&gt;o&lt;/sup&gt; latitudinal extent in the south, which is consistent with MESSENGER observations. We found an anti-correlation in the incidence area on the surface and the incidence particle rate between the northern and southern cusp precipitation such that the total area and the total rate through both of the cusps remain constant and independent of the IMF orientation. We also show that the solar wind proton incidence rate to the entire surface of Mercury is higher when the IMF has a northward component and nearly half of the incidence flux impacts the low latitudes on the nightside. During extreme solar events (e.g., Coronal Mass Ejections) a large area on the dayside surface of Mercury is exposed to the solar wind plasma, especially in the southern hemisphere. Our model suggests that over 70 nPa solar wind dynamic pressure is required for the entire surface of Mercury to be exposed to the solar wind plasma.&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document