Is the Relation Between the Solar Wind Dynamic Pressure and the Magnetopause Standoff Distance so Straightforward?

We present results of global magnetohydrodynamic simulations which reconsider the relationship between the solar wind dynamic pressure (Pd) and magnetopause standoff distance (RSUB). We simulate the magnetospheric response to increases in the dynamic pressure by varying separately the solar wind density or velocity for northward and southward interplanetary magnetic field (IMF). We obtain different values of the power law indices N in the relation RSUB- ¼Pd- 1/N depending on which parameter, density, or velocity, has been varied and for which IMF orientation. The changes in the standoff distance are smaller (higher N) for a density increase for southward IMF and greater (smaller N) for a velocity increase. An enhancement of the solar wind velocity for a southward IMF increases the magnetopause reconnection rate and Region 1 current that move the magnetopause closer to the Earth than it appears in the case of density increase for the same dynamic pressure.Plain Language SummaryThe magnetopause is the boundary between the near- Earth space, which is governed by the magnetic field produced in the Earth’s core, and interplanetary space populated by the plasma emitted from the Sun called the solar wind. It is well known that the position of this boundary is defined by the balance of the pressures from both sides of the magnetopause and in a unique way depends on the velocity and density of the plasma in the interplanetary space. In this work, we reexamine the relationship between the magnetopause position and parameters of the solar wind by means of computer modeling. It is shown that the relationship between solar wind velocity and density and magnetopause position is more complex than originally thought. It is suggested that the pressure balance condition through the magnetopause depends on the continuing magnetic reconnection between the interplanetary and magnetospheric magnetic field lines and that the consequences of the reconnection change the relationship between the solar wind dynamic pressure and magnetopause boundary location.Key PointsWe reconsider the relation between the solar wind dynamic pressure and magnetopause standoff distanceThe magnetopause reacts differently to density, and velocity increases for the same dynamic pressureA new scaling law for magnetopause standoff distance is proposedPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154966/1/grl60461_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154966/2/grl60461.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154966/3/grl60461-sup-0001-Supporting_Information_SI-S01.pd

Three-dimensional magnetic flux rope structure formed by multiple sequential X-line reconnection at the magnetopause

On 14 June 2007, four Time History of Events and Macroscale Interactions during Substorms spacecraft observed a flux transfer event (FTE) on the dayside magnetopause, which has been previously proved to be generated by multiple, sequential X-line reconnection (MSXR) in a 2-D context. This paper reports a further study of the MSXR event to show the 3-D viewpoint based on additional measurements. The 3-D structure of the FTE flux rope across the magnetospheric boundary is obtained on the basis of multipoint measurements taken on both sides of the magnetopause. The flux rope's azimuthally extended section is found to lie approximately on the magnetopause surface and parallel to the X-line direction; while the axis of the magnetospheric branch is essentially along the local unperturbed magnetospheric field lines. In the central region of the flux rope, as distinct from the traditional viewpoint, we find from the electron distributions that two types of magnetic field topology coexist: opened magnetic field lines connecting the magnetosphere and the magnetosheath and closed field lines connecting the Southern and Northern hemispheres. We confirm, therefore, for the first time, the characteristic feature of the 3-D reconnected magnetic flux rope, formed through MSXR, through a determination of the field topology and the plasma distributions within the flux rope. Knowledge of the complex geometry of FTE flux ropes will improve our understanding of solar wind-magnetosphere interaction.Astronomy & AstrophysicsSCI(E)5ARTICLE51904-191111

Cluster observes formation of high-beta plasma blobs

Late in a sequence of four moderate substorms on 26 July 2001, Cluster observed periods of a few minutes durations of high-beta plasma events (<i>B</i><10nT, β=2-30), connected with dipolarizations of the magnetic field. Cluster was located near 02:45 MLT, at <i>R</i>=19<i>R<sub>E</sub></i> and at about 5°N GSM. These events began late in the recovery phase of the second and about 5min before onset of the third substorm and lasted for three hours, way beyond the recovery phase of the fourth substorm. The most remarkable observation is that the onset coincided with the arrival of energetic (<i>E</i>~7keV) O<sup>+</sup> ions and energetic electrons obviously from the ionosphere, which tended to dominate the plasma composition throughout the remaining time. The magnetic flux and plasma transport is continuously directed equatorward and earthward, with oscillatory east-west movements superposed. Periods of the order of 5-10min and strong correlations between the magnetic elevation angle and log β (correlation coefficient 0.78) are highly reminiscent of the high-beta plasma blobs discovered with Equator-S and Geotail between 9 and 11<i>R<sub>E</sub></i> in the late night/early morning sector (Haerendel et al., 1999). <P style="line-height: 20px;"> We conclude that Cluster observed the plasma blob formation in the tail plasma sheet, which seems to occur predominantly in the recovery and post-recovery phases of substorms. This is consistent with the finding of Equator-S and Geotail. The origin is a pulsed earthward plasma transport with velocity amplitudes of only several tens of km/s

Extended magnetic reconnection across the dayside magnetopause

The extent of where magnetic reconnection (MR), the dominant process responsible for energy and plasma transport into the magnetosphere, operates across Earth’s dayside magnetopause has previously been only indirectly shown by observations. We report the first direct evidence of X-line structure resulting from the operation of MR at each of two widely separated locations along the tilted, subsolar line of maximum current on Earth’s magnetopause, confirming the operation of MR at two or more sites across the extended region where MR is expected to occur. The evidence results from in-situ observations of the associated ion and electron plasma distributions, present within each magnetic X-line structure, taken by two spacecraft passing through the active MR regions simultaneously

Long-term variations in solar wind parameters, magnetopause location, and geomagnetic activity over the last five solar cycles

We use both solar wind observations and empirical magnetopause models to reconstruct time series of the magnetopause standoff distance for nearly five solar cycles. Since the average annual interplanetary magnetic field (IMF) Bz is about zero, and the annual IMF cone angle varies between 54.0° and 61.2°, the magnetopause standoff distance on this time scale depends mostly on the solar wind dynamic pressure. The annual IMF magnitude well correlates with the sunspot number (SSN) with a zero time lag, while the annual solar wind dynamic pressure (Pdyn) correlates reasonably well with the SSN but with 3 years time lag. At the same time, we find an anticorrelation between Pdyn and SSN in cycles 20–21 and a correlation in cycles 22–24 with 2 years time lag. Both the annual solar wind density and velocity well correlate with the dynamic pressure, but the correlation coefficient is higher for density than for velocity. The 11‐year solar cycles in the dynamic pressure variations are superimposed by an increasing trend before 1991 and a decreasing trend between 1991 and 2009. The average annual solar wind dynamic pressure decreases by a factor of three from 1991 to 2009. Correspondingly, the predicted standoff distance in Lin et al.’s (2010) magnetopause model increases from 9.7 RE in 1991 to 11.6 RE in 2009. The annual SSN, IMF magnitude and magnetospheric geomagnetic activity indices display the same trends as the dynamic pressure. We calculate extreme solar wind parameters and magnetopause standoff distance in each year using daily values and find that both extremely small and large standoff distances during a solar cycle preferably occur at solar maximum r0061ther than at solar minimum

Interaction of erythrocyte membranes with derivatives of 3-oxypiridines

In connection with the increased interest in the use of auto-erythrocytes for directional drug transport, the study of the ability of erythrocytes to sorb an antioxidant drug is becoming topical. The article considers the method of spectrophotometry developed for evaluating the ability of erythrocytes to load with a mexidol preparation under conditions of natural sorption and a method created for determining the drug concentration in erythrocyte biological medias. Materials and methods. The peripheral blood of 15 clinically healthy males aged 20 to 45 years was used as an object of the study. A pharmaceutical preparation of oxymethylethylpyridine succinate-mexidol (ZAO «Pharmasoft», Russia) was used for clinical studies. The drug belongs to the group of 3-hydroxypyridines. The inclusion of mexidol was carried out by direct incubation of erythrocytes in a medium containing this preparation. The concentrations of the preparation were 1.25,2.5 and 5 ßg/ml and the incubation time was 15,20 and 3o minutes. The supernatant was obtained by centrifugation for 10 minutes at 3000 rpm on a SF-2000 spectrophotometer at a wavelength of 630 nm. In addition to the pharmacopoeial method, the oxidation-reduction reaction of the supernatant with methylene blue was used. Results. When measuring the spectra of the supernatant with different concentration of the preparation and using methylene blue, a regression relationship between mexidol and optical density was established, and the optimal exposure time of red blood cells and the drug was determined. These data can be used to control the directional transport of the drug to target organs. A model of the equation for determination of the mexidol content in biomedids is proposed

USING OF 3D-MICROSCOPY IN MICROSURGERY

Work is executed at RFBR financial support, the project 15-29-04868

Experimental study of nonlinear interaction of plasma flow with charged thin current sheets: 1. Boundary structure and motion

We study plasma transport at a thin magnetopause (MP), described hereafter as a thin current sheet (TCS), observed by Cluster at the southern cusp on 13 February 2001 around 20:01 UT. The Cluster observations generally agree with the predictions of the Gas Dynamic Convection Field (GDCF) model in the magnetosheath (MSH) up to the MSH boundary layer, where significant differences are seen. We find for the MP a normal roughly along the GSE x-axis, which implies a clear departure from the local average MP normal, a ~90 km thickness and an outward speed of 35 km/s. Two populations are identified in the MSH boundary layer: the first one roughly perpendicular to the MSH magnetic field, which we interpret as the &quot;incident&quot; MSH plasma, the second one mostly parallel to <b>B</b>. Just after the MP crossing a velocity jet is observed with a peak speed of 240 km/s, perpendicular to <b>B</b>, with <i>M_A</i>=3 and &beta;>10 (peak value 23). The magnetic field clock angle rotates by 70&deg; across the MP. <i>E_x</i> is the main electric field component on both sides of the MP, displaying a bipolar signature, positive on the MSH side and negative on the opposite side, corresponding to a ~300 V electric potential jump across the TCS. The <i>E</i>&times;<i>B</i> velocity generally coincides with the perpendicular velocity measured by CIS; however, in the speed jet a difference between the two is observed, which suggests the need for an extra flow source. We propose that the MP TCS can act locally as an obstacle for low-energy ions (&lt;350 eV), being transparent for ions with larger gyroradius. As a result, the penetration of plasma by finite gyroradius is considered as a possible source for the jet. The role of reconnection is briefly discussed. The electrodynamics of the TCS along with mass and momentum transfer across it are further discussed in the companion paper by Savin et al. (2006)

Localization of shadow poles by complex scaling

Through numerical examples we show that the complex scaling method is suited to explore the pole structure in multichannel scattering problems. All poles lying on the multisheeted Riemann energy surface, including shadow poles, can be revealed and the Riemann sheets on which they reside can be identified.Comment: 6 pages, Latex with Revtex, 3 figures (not included) available on reques

In-flight calibration of the Cluster PEACE sensors

The Plasma Electron and Current Experiment (PEACE) instruments operate on all four of the Cluster spacecraft and measure the 3-D velocity distribution of electrons in the energy range from 0.59 eV to 26.4 keV during each spacecraft spin. Pitch angle distributions and moments of the velocity distribution are also produced. As the mission has progressed, the efficiency of the detectors has declined. Several factors may play a role in this decline such as exposure to radiation, high electron fluxes and spacecraft thruster firings. To account for these variations, continuous in-flight calibration work is essential. The purpose of this paper is to describe the PEACE calibration parameters, focussing in particular on those that vary over time, and to describe the methods which are used to determine their evolution