Plasma and magnetic field conditions during radar blackouts at Mars.

2021 ◽  
Author(s):  
Mark Lester ◽  
Beatriz Sanchez-Cano ◽  
Hermann Opgenoorth
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Solar Zenith Angle ◽  
Field Conditions ◽  
Local Times ◽  
Plasma Transport ◽  
Interplanetary Coronal Mass Ejections ◽  
Plasma System ◽  
Operational Frequency ◽  
Using Data

<p>Large scale solar wind disturbances such as Interplanetary Coronal Mass Ejections (ICMEs) have a major impact on planetary systems.  At Mars, for example, Solar Energetic Particles released during the process that creates the ICME cause large scale radar blackouts as a result of enhanced ionisation at lower altitudes than normal.  The increased absorption of the radar signals can last for up to 10 – 12 days, depending on the operational frequency of the radar.  These events occur at all latitudes and local times but there does appear to be a peak in occurrence at a solar zenith angle of about 160o, i.e. deep in the tail of the Martian plasma system. Using data from MAVEN, Mars Express and Mars Reconnaissance Orbiter we investigate the background plasma  and magnetic field conditions, which occur at the same time as these events to investigate how the SEP impact on the nightside atmosphere.  This will provide crucial evidence for plasma transport in the Martian system, in particular during the passage of ICMEs.</p>

scholarly journals Magnetic topology of coronal mass ejection events out of the ecliptic: Ulysses/HI-SCALE energetic particle observations

2003 ◽  
Vol 21 (6) ◽  
pp. 1249-1256 ◽  
Author(s):  
O. E. Malandraki ◽  
E. T. Sarris ◽  
G. Tsiropoula
Keyword(s):  
Magnetic Field ◽  
High Latitude ◽  
Energetic Particle ◽  
Large Scale ◽  
Energetic Electron ◽  
Solar Energetic Particle ◽  
Interplanetary Coronal Mass Ejections ◽  
Interplanetary Magnetic Fields ◽  
Interplanetary Physics ◽  
Field Lines

Abstract. Solar energetic particle fluxes (Ee > 38 keV) observed by the ULYSSES/HI-SCALE experiment are utilized as diagnostic tracers of the large-scale structure and topology of the Interplanetary Magnetic Field (IMF) embedded within two well-identified Interplanetary Coronal Mass Ejections (ICMEs) detected at 56° and 62° south heliolatitudes by ULYSSES during the solar maximum southern high-latitude pass. On the basis of the energetic solar particle observations it is concluded that: (A) the high-latitude ICME magnetic structure observed in May 2000 causes a depression in the solar energetic electron intensities which can be accounted for by either a detached or an attached magnetic field topology for the ICME; (B) during the traversal of the out-of-ecliptic ICME event observed in July 2000 energetic electrons injected at the Sun are channeled by the ICME and propagate freely along the ICME magnetic field lines to 62° S heliolatitude.Key words. Interplanetary physics (energetic particles; interplanetary magnetic fields)

Spatial coherence of interplanetary coronal mass ejection-driven sheaths at 1 AU

2020 ◽  
Author(s):  
Matti Ala-Lahti ◽  
Julia Ruohotie ◽  
Simon Good ◽  
Emilia Kilpua ◽  
Noé Lugaz
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Spatial Coherence ◽  
Field Measurements ◽  
Interplanetary Coronal Mass Ejections ◽  
Magnetic Structures ◽  
Interplanetary Coronal Mass Ejection ◽  
Field Fluctuations ◽  
Mass Ejection ◽  
The Magnetic Field

<p><span>We report on the longitudinal coherence of sheath regions driven by interplanetary coronal mass ejections (ICMEs). ICME sheaths are significant drivers of geomagnetic activity at the Earth, with a considerable fraction of ICME-driven storms being either entirely or primarily induced by the sheath. Similarly to Lugaz et al. (2018; doi:10.3847/2041-8213/aad9f4</span><span>), we have analyzed two-point magnetic field measurements made by the ACE and <em>Wind </em>spacecraft in 29 ICME sheaths to estimate the coherence scale lengths, defined as the spatial scale at which correlation between measurements falls to zero, of the field magnitude and components. Scale lengths for the sheath are found to be mostly smaller than the corresponding values in the ICME driver, an expected result given that ICME sheaths are characterized by highly fluctuating, variable magnetic fields, in contrast to the often more coherent ejecta. A relatively large scale length for the magnetic field component in the GSE <em>y</em>-direction was found. We discuss how magnetic field line draping around the ejecta and the alignment of pre-existing magnetic structures by the preceding shock may explain the observed results. In addition, we consider the existence of longitudinally extended and possibly geoeffective magnetic field fluctuations within ICME sheaths, the full understanding of which requires further multi-spacecraft analysis.</span></p>

scholarly journals A model of mid-latitude E-region plasma convergence inside a planetary wave cyclonic vortex

2002 ◽  
Vol 20 (8) ◽  
pp. 1193-1201 ◽  
Author(s):  
S. Shalimov ◽  
C. Haldoupis
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Planetary Wave ◽  
Numerical Solutions ◽  
Lower Thermosphere ◽  
Plasma Transport ◽  
Neutral Wind ◽  
Prevailing Wind Direction ◽  
E Region ◽  
Region Plasma

Abstract. Recently, Shalimov et al. (1999) proposed a new mechanism for large-scale accumulation of long-lived metallic ions in the mid-latitude ionosphere driven by planetary waves in the lower thermosphere. In this mechanism, the combined action of frictional and horizontal magnetic field forces at E-region altitudes causes the plasma to converge and accumulate in large areas of positive neutral wind vorticity within a propagating planetary wave. The present paper provides a theoretical formulation for this mechanism by modelling both horizontal and vertical plasma transport effects within a planetary wave vortex, of cyclonic neutral wind. Non-steady-state numerical solutions of the ion continuity equation show that the proposed accumulation process can enhance the ionization significantly inside the planetary wave vortex but its efficiency depends strongly on altitude, whereas on the other hand, it can be complicated by vertical plasma motions. The latter, which are driven by the same planetary wave wind field under the action of the vertical Lorentz force and meridional wind forcing along the magnetic field lines, can lead to either plasma compressions or depletions, depending on the prevailing wind direction. We conclude that, for shorter times, vertical plasma transport may act constructively to the horizontal gathering process to produce considerable E-region plasma accumulation over large sectors of a planetary wave vortex of cyclonic winds.Key words. Ionosphere (ionosphere-atmosphere interactions; mid-latitude ionosphere; sporadic E-layers) – Meteorology and atmospheric dynamics (waves and tides)

scholarly journals Substorm-associated large-scale magnetic field changes in the magnetotail: a prerequisite for "magnetotail deflation" events

2003 ◽  
Vol 21 (4) ◽  
pp. 869-879 ◽  
Author(s):  
H. Nakai ◽  
Y. Kamide
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Large Scale ◽  
Dynamic Pressure ◽  
Regression Function ◽  
Large Scale Magnetic Field ◽  
Storms And Substorms ◽  
Using Data ◽  
Current Systems ◽  
Component Parallel

Abstract. An attempt is made to search for a critical condition in the lobe magnetic field to initiate large-scale magnetic field changes associated with substorm expansions. Using data from ISEE-1 for 1978, sudden decreases in the lobe magnetic field accompanied by magnetic field dipolarizations are identified. In this study, such events are designated as the magnetotail deflation. The magnetic field component parallel to the equatorial plane, BE , is normalized to a fixed geocentric distance, BEN , and is corrected for the compression effect of the solar wind dynamic pres-sure, BENC . It is shown that the BENC value just prior to a magnetotail deflation correlates well with the Dst index; BENC = 37.5 - 0.217 Dst0, where Dst0 denotes the Dst value corrected for the solar wind dynamic pressure. This regression function appears to delineate the upper limit of BENC values, when they are sorted by the Dst0 index. On the basis of this finding it is suggested that a prerequisite condition for magnetotail deflations must exist in the magnetosphere.Key words. Magnetospheric physics (magnetotail; current systems; storms and substorms)

scholarly journals The intergalactic magnetic field probed by a giant radio galaxy

2019 ◽  
Vol 622 ◽  
pp. A16 ◽  
Author(s):  
S. P. O’Sullivan ◽  
J. Machalski ◽  
C. L. Van Eck ◽  
G. Heald ◽  
M. Brüggen ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Radio Galaxy ◽  
Small Scale ◽  
Cosmological Simulations ◽  
Rotation Measure ◽  
Sky Survey ◽  
Intergalactic Magnetic Field ◽  
Using Data ◽  
The Universe

Cosmological simulations predict that an intergalactic magnetic field (IGMF) pervades the large scale structure (LSS) of the Universe. Measuring the IGMF is important to determine its origin (i.e. primordial or otherwise). Using data from the LOFAR Two Metre Sky Survey (LoTSS), we present the Faraday rotation measure (RM) and depolarisation properties of the giant radio galaxy J1235+5317, at a redshift of z = 0.34 and 3.38 Mpc in size. We find a mean RM difference between the lobes of 2.5 ± 0.1 rad m−2, in addition to small scale RM variations of ∼0.1 rad m−2 . From a catalogue of LSS filaments based on optical spectroscopic observations in the local universe, we find an excess of filaments intersecting the line of sight to only one of the lobes. Associating the entire RM difference to these LSS filaments leads to a gas density-weighted IGMF strength of ∼0.3 μG. However, direct comparison with cosmological simulations of the RM contribution from LSS filaments gives a low probability (∼5%) for an RM contribution as large as 2.5 rad m−2, for the case of IGMF strengths of 10–50 nG. It is likely that variations in the RM from the Milky Way (on 11′ scales) contribute significantly to the mean RM difference, and a denser RM grid is required to better constrain this contribution. In general, this work demonstrates the potential of the LOFAR telescope to probe the weak signature of the IGMF. Future studies, with thousands of sources with high accuracy RMs from LoTSS, will enable more stringent constraints on the nature of the IGMF.

scholarly journals Spacecraft Reveal New Details of Magnetic Reconnection

Eos ◽  
2021 ◽  
Vol 102 ◽  
Author(s):  
Morgan Rehnberg
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Large Scale ◽  
Field Conditions ◽  
Energetic Electrons ◽  
Large Scale Magnetic Field

Energetic electrons are accelerated directly by magnetic reconnections and can act as tracers of large-scale magnetic field conditions.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

Polar Magnetic Field Reversals of the Sun in Maunder Minimum

2000 ◽  
Vol 179 ◽  
pp. 193-196
Author(s):  
V. I. Makarov ◽  
A. G. Tlatov
Keyword(s):  
Magnetic Field ◽  
Maunder Minimum ◽  
The Sun ◽  
Annual Rings ◽  
Field Reversal ◽  
Polar Magnetic Field ◽  
Pine Trees ◽  
Using Data ◽  
Magnetic Field Reversal

AbstractA possible scenario of polar magnetic field reversal of the Sun during the Maunder Minimum (1645–1715) is discussed using data of magnetic field reversals of the Sun for 1880–1991 and the14Ccontent variations in the bi-annual rings of the pine-trees in 1600–1730 yrs.

Student Perceptions of Community: A Different Perspective

NASPA Journal ◽  
1998 ◽  
Vol 35 (4) ◽  
Author(s):  
Jackie Clark ◽  
Joan Hirt
Keyword(s):  
Student Perceptions ◽  
Large Scale ◽  
Research University ◽  
Small Scale ◽  
Social Environments ◽  
Common Assumption ◽  
Small Communities ◽  
Public Research University ◽  
The Common ◽  
Using Data

The creation of small communities has been proposed as a way of enhancing the educational experience of students at large institutions. Using data from a survey of students living in large and small residences at a public research university, this study does not support the common assumption that small-scale social environments are more conducive to positive community life than large-scale social environments.

scholarly journals An 84-μG Magnetic Field in a Galaxy at Z=0.692?

2008 ◽  
Vol 4 (S254) ◽  
pp. 95-96
Author(s):  
Arthur M. Wolfe ◽  
Regina A. Jorgenson ◽  
Timothy Robishaw ◽  
Carl Heiles ◽  
Jason X. Prochaska
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Faraday Rotation ◽  
Large Scale ◽  
Dynamo Model ◽  
Magnetic Field Generation ◽  
Interstellar Gas ◽  
Splitting Technique ◽  
Average Value ◽  
The Magnetic Field

AbstractThe magnetic field pervading our Galaxy is a crucial constituent of the interstellar medium: it mediates the dynamics of interstellar clouds, the energy density of cosmic rays, and the formation of stars (Beck 2005). The field associated with ionized interstellar gas has been determined through observations of pulsars in our Galaxy. Radio-frequency measurements of pulse dispersion and the rotation of the plane of linear polarization, i.e., Faraday rotation, yield an average value B ≈ 3 μG (Han et al. 2006). The possible detection of Faraday rotation of linearly polarized photons emitted by high-redshift quasars (Kronberg et al. 2008) suggests similar magnetic fields are present in foreground galaxies with redshifts z > 1. As Faraday rotation alone, however, determines neither the magnitude nor the redshift of the magnetic field, the strength of galactic magnetic fields at redshifts z > 0 remains uncertain.Here we report a measurement of a magnetic field of B ≈ 84 μG in a galaxy at z =0.692, using the same Zeeman-splitting technique that revealed an average value of B = 6 μG in the neutral interstellar gas of our Galaxy (Heiles et al. 2004). This is unexpected, as the leading theory of magnetic field generation, the mean-field dynamo model, predicts large-scale magnetic fields to be weaker in the past, rather than stronger (Parker 1970).The full text of this paper was published in Nature (Wolfe et al. 2008).

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