scholarly journals Occurrence rate of ultra-low frequency waves in the foreshock of Mercury increases with heliocentric distance

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
N. Romanelli ◽  
G. A. DiBraccio
Keyword(s):  
Solar Wind ◽  
Heliocentric Distance ◽  
Low Frequency ◽  
Occurrence Rate ◽  
Eccentric Orbit ◽  
Low Intensity ◽  
Magnetometer Data ◽  
Favorable Conditions ◽  
Open Question ◽  
Low Frequency Waves

AbstractStudies of Mercury’s foreshock have analyzed in detail the properties of ultra-low frequency waves. However, an open question remains in regards to understanding favorable conditions for these planetary foreshocks waves. Here, we report that 0.05–0.41 Hz quasi-monochromatic waves are mostly present under quasi-radial and relatively low intensity Interplanetary Magnetic Field, based on 17 Mercury years of MESSENGER Magnetometer data. These conditions are consistent with larger foreshock size and reflection of solar wind protons, their most likely source. Consequently, we find that the wave occurrence rate increases with Mercury’s heliocentric distance. Detection of these waves throughout Mercury’s highly eccentric orbit suggests the conditions for backstreaming protons are potentially present for all of Mercury’s heliocentric distances, despite the relatively low solar wind Alfvén Mach number regime. These results are relevant for planetary magnetospheres throughout the solar system, and the magnetospheres of exoplanets, and provide knowledge of particle acceleration mechanisms occurring inside foreshocks.

scholarly journals Upstream Ultra-Low Frequency Waves Observed by MESSENGER's Magnetometer: Implications for Particle Acceleration at Mercury's Bow Shock

2020 ◽  
Author(s):  
Norberto Romanelli ◽  
Gina DiBraccio ◽  
Daniel Gershman ◽  
Guan Le ◽  
Christian Mazelle ◽  
...  
Keyword(s):  
Solar Wind ◽  
Wave Amplitude ◽  
Solar Wind Speed ◽  
Low Frequency ◽  
Space Environment ◽  
Occurrence Rate ◽  
Frequency Range ◽  
S Waves ◽  
Mercury Surface ◽  
Low Frequency Waves

<p>In this work we perform the first statistical analysis of the main properties of waves observed in the 0.05–0.41 Hz frequency range in the Hermean foreshock by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Magnetometer. Although we find similar polarization properties to the '30 s' waves observed at the Earth's foreshock, the normalized wave amplitude (∼0.2) and occurrence rate (∼0.5%) are much smaller. This suggests significant lower backstreaming proton fluxes, due to the relatively low solar wind Alfvenic Mach number around Mercury. These differences could also be related to the relatively smaller foreshock size and/or more variable solar wind conditions. Furthermore, we estimate that the speed of resonant backstreaming protons in the solar wind reference frame (likely source for these waves) ranges between 0.95 and 2.6 times the solar wind speed. The closeness between this range and what is observed at other planetary foreshocks suggests that similar acceleration processes are responsible for this energetic population and might be present in the shocks of exoplanets.</p>

scholarly journals 49. The Interplanetary Plasma and the Heliosphere

1979 ◽  
Vol 17 (1) ◽  
pp. 199-213
Author(s):  
A. Hewish
Keyword(s):  
Solar Wind ◽  
Heliocentric Distance ◽  
Solar Magnetic Field ◽  
Interplanetary Space ◽  
Low Frequency ◽  
Surface Heat ◽  
Solar Origin ◽  
Interplanetary Plasma ◽  
Principal Energy ◽  
Low Frequency Waves

It is now generally recognized that the solar wind represents that part of the solar corona which is not confined by the solar magnetic field, and therefore escapes into interplanetary space. The escaping gas is heated by sources of solar origin (presumably low frequency waves) to about 2 x 106 K within a distance less than (1/20) R from the sun’s surface; although the solar wind temperature decreases thereafter, heating sources may continue to act through 1 a.u. heliocentric distance. A transition from subsonic to supersonic flow occurs within a few solar radii of the sun’s surface, heat conduction representing the principal energy supply for the acceleration of the solar wind. However, additional accelerating processes may also be active.

Low-frequency waves in the solar wind near Neptune

1991 ◽  
Vol 18 (6) ◽  
pp. 1071-1074 ◽  
Author(s):  
Ming Zhang ◽  
J. W. Belcher ◽  
J. D. Richardson ◽  
V. M. Vasyliunas ◽  
R. P. Lepping ◽  
...  
Keyword(s):  
Solar Wind ◽  
Low Frequency ◽  
Low Frequency Waves

scholarly journals Magnetic holes in the solar wind between 0.3 AU and 17 AU

2000 ◽  
Vol 7 (3/4) ◽  
pp. 191-200 ◽  
Author(s):  
K. Sperveslage ◽  
F. M. Neubauer ◽  
K. Baumgärtel ◽  
N. F. Ness
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Heliocentric Distance ◽  
Occurrence Rate ◽  
Automatic Identification ◽  
Soliton Theory ◽  
Theoretical Approaches ◽  
Maximum Angle ◽  
Using Data ◽  
Initial Magnetic Field

Abstract. Magnetic holes (MHs) are depressions of the magnetic field magnitude. Turner et al. (1977) identified the first MHs in the solar wind and determined an occurrence rate of 1.5 MHs/d. Winterhalter et al. (1994) developed an automatic identification criterion to search for MHs in Ulysses data in the solar wind between 1 AU and 5.4 AU. We adopt their criterion to expand the search to the heliocentric distances down to 0.3 AU using data from Helios 1 and 2 and up to 17 AU using data from Voyager 2. We relate our observations to two theoretical approaches which describe the so-called linear MHs in which the magnetic vector varies in magnitude rather than direction. Therefore we focus on such linear MHs with a directional change less than 10º. With our observations of about 850 MHs we present the following results: Approximately 30% of all the identified MHs are linear. The maximum angle between the initial magnetic field vector and any vector inside the MH is 20º in average and shows a weak relation to the depth of the MHs. The angle between the initial magnetic field and the minimum variance direction of those structures is large and very probably close to 90º. The MHs are placed in a high β environment even though the average solar wind shows a smaller β. The widths decrease from about 50 proton inertial length in a region between 0.3 AU and 0.4 AU heliocentric distance to about 15 proton inertial length at distances larger than 10 AU. This quantity is correlated with the β of the MH environments with respect to the heliocentric distance. There is a clear preference for the occurrence of depressions instead of compressions. We discuss these results with regard to the main theories of MHs, the mirror instability and the alternative soliton approach. Although our observational results are more consistent with the soliton theory we favour a combination of both. MHs might be the remnants of initial mirror mode structures which can be described as solitons during the main part of their lifetime.

scholarly journals Model for vortex turbulence with discontinuities in the solar wind

2003 ◽  
Vol 10 (4/5) ◽  
pp. 335-343 ◽  
Author(s):  
O. P. Verkhoglyadova ◽  
B. Dasgupta ◽  
B. T. Tsurutani
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
High Speed ◽  
Vector Fields ◽  
Field Vector ◽  
Theoretical Modelling ◽  
Occurrence Rate ◽  
Embedded Discontinuities ◽  
Magnetometer Data ◽  
Speed Solar Wind

Abstract. A model of vortex with embedded discontinuities in plasma flow is developed in the framework of ideal MHD in a low b plasma. Vortex structures are considered as a result of 2-D evolution of nonlinear shear Alfvén waves in the heliosphere. Physical properties of the solutions and vector fields are analyzed and the observational aspects of the model are discussed. The ratio of normal components to the discontinuity Br /Vr can be close to -2. The alignment between velocity and magnetic field vectors takes place. Spacecraft crossing such vortices will typically observe a pair of discontinuities, but with dissimilar properties. Occurrence rate for different discontinuity types is estimated and agrees with observations in high-speed solar wind stream. Discontinuity crossing provides a backward rotation of magnetic field vector and can be observed as part of a backward arc. The Ulysses magnetometer data obtained in the fast solar wind are compared with the results of theoretical modelling.

EXCITATION OF LOW-FREQUENCY WAVES IN THE SOLAR WIND BY NEWBORN INTERSTELLAR PICKUP IONS H+AND He+AS SEEN BY VOYAGER AT 4.5 AU

2010 ◽  
Vol 724 (2) ◽  
pp. 1256-1261 ◽  
Author(s):  
Colin J. Joyce ◽  
Charles W. Smith ◽  
Philip A. Isenberg ◽  
Neil Murphy ◽  
Nathan A. Schwadron
Keyword(s):  
Solar Wind ◽  
Low Frequency ◽  
Pickup Ions ◽  
Low Frequency Waves

Association of low-frequency waves with suprathermal ions in the upstream solar wind

1979 ◽  
Vol 6 (3) ◽  
pp. 209-212 ◽  
Author(s):  
G. Paschmann ◽  
N. Sckopke ◽  
S. J. Bame ◽  
J. R. Asbridge ◽  
J. T. Gosling ◽  
...  
Keyword(s):  
Solar Wind ◽  
Low Frequency ◽  
Suprathermal Ions ◽  
Upstream Solar Wind ◽  
Low Frequency Waves

scholarly journals Statistical study of foreshock cavitons

2013 ◽  
Vol 31 (12) ◽  
pp. 2163-2178 ◽  
Author(s):  
P. Kajdič ◽  
X. Blanco-Cano ◽  
N. Omidi ◽  
K. Meziane ◽  
C. T. Russell ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Statistical Study ◽  
Low Frequency ◽  
Bow Shock ◽  
Occurrence Rate ◽  
Time Intervals ◽  
Distinct Structure ◽  
Wide Range ◽  
The Magnetic Field

Abstract. In this work we perform a statistical analysis of 92 foreshock cavitons observed with the Cluster spacecraft 1 during the period 2001–2006. We analyze time intervals during which the spacecraft was located in the Earth's foreshock with durations longer than 10 min. Together these amount to ~ 50 days. The cavitons are transient structures in the Earth's foreshock. Their main signatures in the data include simultaneous depletions of the magnetic field intensity and plasma density, which are surrounded by a rim of enhanced values of these two quantities. Cavitons form due to nonlinear interaction of transverse and compressive ultra-low frequency (ULF) waves and are therefore always surrounded by intense compressive ULF fluctuations. They are carried by the solar wind towards the bow shock. This work represents the first systematic study of a large sample of foreshock cavitons. We find that cavitons appear for a wide range of solar wind and interplanetary magnetic field conditions and are therefore a common feature upstream of Earth's quasi-parallel bow shock with an average occurrence rate of ~ 2 events per day. We also discuss their observational properties in the context of other known upstream phenomena and show that the cavitons are a distinct structure in the foreshock.

scholarly journals ULF waves in Ganymede's upstream magnetosphere

2013 ◽  
Vol 31 (1) ◽  
pp. 45-59 ◽  
Author(s):  
M. Volwerk ◽  
X. Jia ◽  
C. Paranicas ◽  
W. S. Kurth ◽  
M. G. Kivelson ◽  
...  
Keyword(s):  
Field Line ◽  
Low Frequency ◽  
Theoretical Models ◽  
Closed Field ◽  
Field Line Resonances ◽  
Line Region ◽  
Magnetometer Data ◽  
Closed Field Line ◽  
Using Data ◽  
Low Frequency Waves

Abstract. Ganymede's mini-magnetosphere, embedded in Jupiter's larger one, sustains ULF (ultra-low frequency) waves that are analyzed here using data from two Galileo flybys that penetrate deeply into the upstream closed field line region. The magnetometer data are used to identify field line resonances, magnetopause waves and ion cyclotron waves. The plasma densities that are inferred from the interpretation of these waves are compared with the observations made by other plasma and wave experiments on Galileo and with numerical and theoretical models of Ganymede's magnetosphere.

Ultra-low frequency foreshock waves at Venus and Mercury in a global hybrid simulation

2020 ◽  
Author(s):  
Riku Jarvinen ◽  
Esa Kallio ◽  
Tuija I. Pulkkinen
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Large Scale ◽  
Low Frequency ◽  
Hybrid Simulation ◽  
Bow Shock ◽  
Upstream Region ◽  
Ulf Waves ◽  
Solar Wind Interaction ◽  
Low Frequency Waves

<p>We study the solar wind interaction with Venus and Mercury in a 3-dimensional global hybrid simulation where ions are treated as particles and electrons are a charge-neutralizing fluid. We concentrate on the formation of large-scale ultra-low frequency (ULF) waves in ion foreshocks and their dependence on the solar wind and interplanetary magnetic field conditions. The ion foreshock forms in the upstream region ahead of the quasi-parallel bow shock, where the angle between the shock normal and the magnetic field is smaller than about 45 degrees. The magnetic connection with the bow shock allows backstreaming of the solar wind ions leading to the formation of the ion foreshock. This kind of beam-plasma configuration is a source of free energy for the excitation of plasma waves. The foreshock ULF waves convect downstream with the solar wind flow and encounter the bow shock. We compare the waves between Venus and Mercury, and analyze the coupling of the ULF waves with the planetary ion acceleration at Venus.</p> <p>References:</p> <p>Jarvinen R., Alho M., Kallio E., Pulkkinen T.I., 2020, Oxygen Ion Escape From Venus Is Modulated by Ultra-Low Frequency Waves, Geophys. Res. Lett., 47, 11, doi:10.1029/2020GL087462</p> <p>Jarvinen R., Alho M., Kallio E., Pulkkinen T.I., 2020, Ultra-low frequency waves in the ion foreshock of Mercury: A global hybrid modeling study, Mon. Notices Royal Astron. Soc., 491, 3, 4147-4161, doi:10.1093/mnras/stz3257</p>

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