scholarly journals Effect of the exoplanet magnetic field topology on its magnetospheric radio emission

2018 ◽  
Vol 616 ◽  
pp. A182 ◽  
Author(s):  
J. Varela ◽  
V. Réville ◽  
A. S. Brun ◽  
P. Zarka ◽  
F. Pantellini
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Interplanetary Magnetic Field ◽  
Stellar Wind ◽  
Scaling Laws ◽  
Dynamic Pressure ◽  
Radio Emissions ◽  
Poynting Flux ◽  
Magnetic Field Topology ◽  
Study Results

Context. The magnetized wind from stars that impact exoplanets should lead to radio emissions. According to the scaling laws derived in the solar system, the radio emission should depend on the stellar wind, interplanetary magnetic field, and topology of the exoplanet magnetosphere. Aims. The aim of this study is to calculate the dissipated power and subsequent radio emission from exoplanet magnetospheres with different topologies perturbed by the interplanetary magnetic field and stellar wind, to refine the predictions from scaling laws, and to prepare the interpretation of future radio detections. Methods. We use the magnetohydrodynamic (MHD) code PLUTO in spherical coordinates to analyze the total radio emission level resulting from the dissipation of the kinetic and magnetic (Poynting flux) energies inside the exoplanet’s magnetospheres. We apply a formalism to infer the detailed contribution in the exoplanet radio emission on the exoplanet’s day side and magnetotail. The model is based on Mercury-like conditions, although the study results are extrapolated to exoplanets with stronger magnetic fields, providing the lower bound of the radio emission. Results. The predicted dissipated powers and resulting radio emissions depend critically on the exoplanet magnetosphere topology and interplanetary magnetic field (IMF) orientation. The radio emission on the exoplanet’s night and day sides should thus contain information on the exoplanet magnetic field topology. In addition, if the topology of an exoplanet magnetosphere is known, the radio emission measurements can be used as a proxy of the instantaneous dynamic pressure of the stellar wind, IMF orientation, and intensity.

scholarly journals Effect of geomagnetic activity, solar wind and parameters of interplanetary magnetic field on regularities in intermittency of Pi2 geomagnetic pulsations

2015 ◽  
Vol 1 (3) ◽  
pp. 11-20 ◽  
Author(s):  
Надежда Куражковская ◽  
Nadezhda Kurazhkovskaya ◽  
Борис Клайн ◽  
Boris Klain
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Activity ◽  
Dynamic Pressure ◽  
Cumulative Distribution ◽  
Qualitative Assessment ◽  
Geomagnetic Pulsations ◽  
Magnetospheric Substorms ◽  
Pi2 Pulsations

We present the results of investigation of the influence of geomagnetic activity, solar wind and parameters of the interplanetary magnetic field (IMF) on properties of the intermittency of midlatitude burst series of Pi2 geomagnetic pulsations observed during magnetospheric substorms on the nightside (substorm Pi2) and in the absence of these phenomena (nonsub-storm Pi2). We considered the index α as a main characteristic of intermittency of substorm and nonsubstorm Pi2 pulsations. The index α characterizes the slope of the cumulative distribution function of Pi2 burst amplitudes. The study indicated that the value and dynamics of the index α varies depending on the planetary geomagnetic activity, auroral activity and the intensity of magnetospheric ring currents. In addition, the forms of dependences of the index α on the density n, velocity V, dynamic pressure Pd of the solar wind and IMF Bx-component are different. The behavior of the index α depending on the module of B, By- and Bz-components is similar. We found some critical values of V, Pd, B, By- and Bz-components, after reaching of which the turbulence of the magnetotail plasma during substorm development is decreased. The revealed patterns of the intermittency of Pi2 pulsations can be used for qualitative assessment of turbulence level in the magnetotail plasma depending on changing interplanetary conditions.

scholarly journals PERIODIC RADIO EMISSION FROM THE M7 DWARF 2MASS J13142039+1320011: IMPLICATIONS FOR THE MAGNETIC FIELD TOPOLOGY

2011 ◽  
Vol 741 (1) ◽  
pp. 27 ◽  
Author(s):  
M. McLean ◽  
E. Berger ◽  
J. Irwin ◽  
J. Forbrich ◽  
A. Reiners
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Magnetic Field Topology ◽  
The Magnetic Field

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 Cluster survey of the mid-altitude cusp: 1. size, location, and dynamics

2006 ◽  
Vol 24 (11) ◽  
pp. 3011-3026 ◽  
Author(s):  
F. Pitout ◽  
C. P. Escoubet ◽  
B. Klecker ◽  
H. Rème
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Time Delay ◽  
Interplanetary Magnetic Field ◽  
Statistical Study ◽  
Proper Time ◽  
Dynamic Pressure ◽  
Solar Wind Dynamic Pressure ◽  
Summer Hemisphere ◽  
External Conditions

Abstract. We present a statistical study of four years of Cluster crossings of the mid-altitude cusp. In this first part of the study, we start by introducing the method we have used a) to define the cusp properties, b) to sort the interplanetary magnetic field (IMF) conditions or behaviors into classes, c) to determine the proper time delay between the solar wind monitors and Cluster. Out of the 920 passes that we have analyzed, only 261 fulfill our criteria and are considered as cusp crossings. We look at the size, location and dynamics of the mid-altitude cusp under various IMF orientations and solar wind conditions. For southward IMF, Bz rules the latitudinal dynamics, whereas By governs the zonal dynamics, confirming previous works. We show that when |By| is larger than |Bz|, the cusp widens and its location decorrelates from By. We interpret this feature in terms of component reconnection occurring under By-dominated IMF. For northward IMF, we demonstrate that the location of the cusp depends primarily upon the solar wind dynamic pressure and upon the Y-component of the IMF. Also, the multipoint capability of Cluster allows us to conclude that the cusp needs typically more than ~20 min to fully adjust its location and size in response to changes in external conditions, and its speed is correlated to variations in the amplitude of IMF-Bz. Indeed, the velocity in °ILAT/min of the cusp appears to be proportional to the variation in Bz in nT: Vcusp=0.024 ΔBz. Finally, we observe differences in the behavior of the cusp in the two hemispheres. Those differences suggest that the cusp moves and widens more freely in the summer hemisphere.

scholarly journals Azimuthally asymmetric ring current as a function of <i>D<sub>st</sub></i> and solar wind conditions

2004 ◽  
Vol 22 (8) ◽  
pp. 2989-2996 ◽  
Author(s):  
Y. P. Maltsev ◽  
A. A. Ostapenko
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Spatial Distribution ◽  
Interplanetary Magnetic Field ◽  
Ring Current ◽  
Dynamic Pressure ◽  
Solar Wind Dynamic Pressure ◽  
Magnetic Data ◽  
Under Five ◽  
Solar Wind Parameters

Abstract. Based on magnetic data, spatial distribution of the westward ring current flowing at |z|<3 RE has been found under five levels of Dst, five levels of the interplanetary magnetic field (IMF) z component, and five levels of the solar wind dynamic pressure Psw. The maximum of the current is located near midnight at distances 5 to 7 RE. The magnitude of the nightside and dayside parts of the westward current at distances from 4 to 9 RE can be approximated as Inight=1.75-0.041 Dst, Inoon=0.22-0.013 Dst, where the current is in MA. The relation of the nightside current to the solar wind parameters can be expressed as Inight=1.45-0.20 Bs IMF + 0.32 Psw, where BsIMF is the IMF southward component. The dayside ring current poorly correlates with the solar wind parameters.

The Influence of Interplanetary Magnetic Field Direction on Martian Crustal Magnetic Field Topology

2020 ◽  
Vol 47 (19) ◽  
Author(s):  
Tristan Weber ◽  
David Brain ◽  
Shaosui Xu ◽  
David Mitchell ◽  
Jared Espley ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Field Direction ◽  
Magnetic Field Direction ◽  
Magnetic Field Topology

Magnetic field within magnetosheath jets during northward and southward interplanetary magnetic field conditions

2020 ◽  
Author(s):  
Laura Vuorinen ◽  
Heli Hietala ◽  
Ferdinand Plaschke
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Dynamic Pressure ◽  
Time History ◽  
Magnetic Shear ◽  
History Of ◽  
High Dynamic ◽  
The Magnetic Field ◽  
Magnetopause Reconnection

&lt;p&gt;Downstream of the Earth's quasi-parallel shock, transients with higher earthward velocities than the surrounding magnetosheath plasma are often observed. These transients have been named magnetosheath jets. Due to their high dynamic pressure, jets can cause multiple types of effects when colliding into the magnetopause. Recently, jets have been linked to triggering magnetopause reconnection in case studies by Hietala et al. (2018) and Nykyri et al. (2019). Jets have been proposed to affect magnetopause reconnection in multiple ways. Jets can compress the magnetopause and make it thin enough for reconnection to occur. Jets could also affect the magnetic shear either by indenting the magnetopause or via the magnetic field of the jets themselves. Here we want to study whether the magnetic field of jets can statistically affect magnetopause reconnection. In particular, we are interested in whether jets could enhance reconnection during more quiet northward IMF conditions.&lt;/p&gt;&lt;p&gt;We statistically study the magnetic field within jets in the subsolar magnetosheath using measurements from the five Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft and OMNI solar wind data from 2008&amp;#8211;2011. We investigate jets next to the magnetopause and find that the magnetic field within jets is statistically different compared to the non-jet magnetosheath. Our results suggest that during southward IMF, the non-jet magnetosheath magnetic field itself has more variation than the jets. This suggests that jets should have no statistical, neither enhancing nor suppressing, effect on reconnection during southward IMF. However, during northward IMF, the magnetic field within jets is statistically favorable for enhancing magnetic reconnection at the subsolar magnetopause as around 70 % of these jets exhibit southward fields close to the magnetopause.&lt;/p&gt;

scholarly journals Tuning in to the radio environment of HD189733b

2019 ◽  
Vol 15 (S354) ◽  
pp. 305-309
Author(s):  
R. D. Kavanagh ◽  
A. A. Vidotto ◽  
D. Ó Fionnagáin ◽  
V. Bourrier ◽  
R. Fares ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Flux Density ◽  
Stellar Wind ◽  
Planetary Orbit ◽  
Close Proximity ◽  
Peak Flux ◽  
Detection Capabilities ◽  
Reconstructed Surface ◽  
Hot Jupiter

AbstractThe hot Jupiter HD189733b is expected to be a source of strong radio emission, due to its close proximity to its magnetically active host star. Here, we model the stellar wind of its host star, based on reconstructed surface stellar magnetic field maps. We use the local stellar wind properties at the planetary orbit obtained from our models to compute the expected radio emission from the planet. Our findings show that the planet emits with a peak flux density within the detection capabilities of LOFAR. However, due to absorption by the stellar wind itself, this emission may be attenuated significantly. We show that the best time to observe the system is when the planet is near primary transit of the host star, as the attenuation from the stellar wind is lowest in this region.

scholarly journals Saturation of the magnetosphere during superstorms: new results from magnetogram inversion technique

2017 ◽  
Vol 3 (3) ◽  
pp. 15-19
Author(s):  
Владимир Мишин ◽  
Vladimir Mishin ◽  
Юрий Караваев ◽  
Yuriy Karavaev
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Flux ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Field ◽  
Dynamic Pressure ◽  
Magnetic Clouds ◽  
Polar Cap ◽  
Thermal Pressure ◽  
Dayside Magnetopause

From data of three three superstorms we study new features of the saturation process of the polar cap magnetic flux deceleration of its area at strengthening the solar wind (SW). It is shown that the saturation of the polar cap is observed at growth of the SW dynamic pressure and vertical IMF component for both signs. Saturation is realized not only during the passage of interplanetary magnetic clouds, but also at significant enhancement of SW density, when the SW thermal pressure is comparable with the pressure of the interplanetary magnetic field. We assume that at such condiitions the saturation is caused not only by a decrease in the efficiency of reconnection at the dayside magnetopause, but mainly by a finite magnetosphere compressibility –stopping the magnetopause compression due to the rapid Eathward growth of the geomagnetic field, ie, interior magnetospheric structure of the geomagnetic field

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