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 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.

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

Long standing waves in a curved canal

1968 ◽  
Vol 34 (4) ◽  
pp. 759-768 ◽  
Author(s):  
B. Johns ◽  
A. M. O. Hamzah
Keyword(s):  
Water Waves ◽  
Wave Amplitude ◽  
Standing Waves ◽  
Low Frequency ◽  
Local Wave ◽  
Low Frequency Waves ◽  
Transverse Oscillations

The dynamics of long water waves are considered in a curved geometry representing a canal bend. The presence of the bend is found to produce a spectrum of transverse oscillations in the canal. The associated dominant amplitudes are evaluated for both tidal periods and higher frequencies representative of tsunamis. It is found that low-frequency waves do not lead to significant transverse amplitudes. For tsunamis, the presence of the bend may result in considerable changes in the local wave amplitude.

Evaluation of an Extended Operational Boussinesq-Type Wave Model for Calculating Low-Frequency Waves in Intermediate Depths

2011 ◽  
Author(s):  
Martijn P. C. de Jong ◽  
Mart Borsboom ◽  
Jan A. M. de Bont ◽  
Bas van Vossen
Keyword(s):  
Low Frequency ◽  
Wave Model ◽  
Coastal Engineering ◽  
Extended Model ◽  
Depth Range ◽  
Frequency Range ◽  
Frequency Wave ◽  
Type Wave ◽  
Wave Heights ◽  
Low Frequency Waves

The motions of (LNG) vessels moored offshore at depths ranging from about 20 to 100 m may depend significantly on the presence of (bound) low-frequency waves with periods in the order of 100 s. This is because these moored vessels show a large motion response in this frequency range and because the energy contents of low-frequency waves at these ‘intermediate’ depths is relatively large. As part of the Joint Industry Project HawaI, the operational Boussinesq-type wave model of Deltares, TRITON, was used to investigate whether this type of wave models could predict bound low-frequency waves (setdown waves) at intermediate depths. Comparison to measured and theoretical data, however, showed an underestimation of the computed levels of bound low-frequency wave heights for this depth range by a factor 2 to 4. Recently, additional tests were made with TRITON in situations for which the model has been designed: coastal engineering applications in shallow water (depths up to at most 20 m). These also showed an underestimation of the bound low-frequency wave heights, albeit smaller, up to a factor 2. In view of the importance of the energy contained in the low-frequency range for certain nearshore and shoreline processes, such as morphological processes, this underestimation is also of concern in coastal engineering. This triggered the development of a higher-order extension of the TRITON model equations (Borsboom, 2008, Wellens, 2010), with the aim to improve the accuracy of the model for long waves while still keeping computational times within acceptable (operational) limits. This paper reports on the usefulness of the extended model for the field of application considered in JIP HawaI/II: providing wave data for calculating the motions of vessels moored in intermediate depths. The results show a significant improvement of the modeling of nonlinear wave dynamics, including the prediction of bound low-frequency waves. This means that the model extension is an important step towards an operational Boussinesq-type wave model with sufficient accuracy in both the wave-frequency (sea, swell) and the low-frequency range for applications in intermediate depths.

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

Predicting heliospheric propagation of CMEs with probabilistic Drag-Based Ensemble Model (DBEM)

2020 ◽  
Author(s):  
Jaša Čalogović ◽  
Mateja Dumbović ◽  
Bojan Vršnak ◽  
Davor Sudar ◽  
Manuela Temmer ◽  
...  
Keyword(s):  
Solar Wind ◽  
Space Weather ◽  
Solar Wind Speed ◽  
Input Parameter ◽  
Source Region ◽  
Space Environment ◽  
Computational Time ◽  
Ensemble Model ◽  
The Earth ◽  
Input Parameters

<p><span>Understanding space weather driven by the solar activity is crucial as it can affect various human technologies, health as well as it can have important implications for the space environment near the Earth and the Earth’s atmosphere. In order to better asses space weather forecasts various empirical, drag-based and MHD models have been developed to predict the arrival time of CMEs. One of them is the analytical Drag-based Model (DBM) applying the equation of CME motion which is determined by the drag force from the background solar wind acting on the CME. DBM predictions depend on various initial parameters such as CME launch speed, background solar wind speed and empirically derived drag parameter as well CME’s angular half-width and longitude of CME source region for a DBM CME cone geometry. Since many of input parameters may be inaccurate or unreliable due to limited observations, the Drag-Based Ensemble Model (DBEM) was developed that considers the variability of model input parameters by making an ensemble of a number of different input parameters to calculate a distribution and significance of DBM results. DBM has the advantage of having very short computational time (< 0.01s) and DBEM ensemble runs with many thousand members can be performed within few seconds on a normal computer. Using such approach, DBEM can determine the most likely CME arrival times and speeds, quantify the prediction uncertainties and calculate the forecast confidence intervals. Recently, DBEM web interface was also integrated as one of the ESA Space Situational Awareness web portal space weather services (http://swe.ssa.esa.int/heliospheric-weather). We’ll present the recent DBEM developments together with the validation of its predictions using observations and other models as well as the input parameter sensitivity tests.</span></p>

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.

Control of terrestrial low frequency bursts by solar wind speed

1996 ◽  
Vol 23 (10) ◽  
pp. 1251-1254 ◽  
Author(s):  
M. D. Desch ◽  
M. L. Kaiser ◽  
W. M. Farrell
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Solar Wind Speed ◽  
Low Frequency

scholarly journals Low frequency geomagnetic field fluctuations at low latitude during the passage of a higher pressure solar wind region

1997 ◽  
Vol 15 (6) ◽  
pp. 656-661
Author(s):  
U. Villante ◽  
P. Francia
Keyword(s):  
Solar Wind ◽  
Geomagnetic Field ◽  
Low Frequency ◽  
Frequency Range ◽  
Low Latitude ◽  
Wind Region ◽  
Spectral Peaks ◽  
Field Fluctuations ◽  
Term Analysis

Abstract. The passage of a higher pressure solar wind region at the Earth's orbit marked the onset of low latitude (L=1.6) fluctuations in the frequency range (0.8–5.5 mHz) for both the horizontal geomagnetic field components. Spectral peaks mostly occur at the same frequencies as the spectral enhancements which appeared in the long term analysis of experimental measurements from the same station and were tentatively interpreted in terms of ground signatures of global magnetospheric modes. A comparison with simultaneous observations discussed by previous investigations allows us to conclude that the same set of frequencies is enhanced in a wide portion of the Earth's magnetosphere.

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