On the Meteoric Smoke Particle Detector SPID: Measurements and analysis from the G-chaser rocket campaign

The Smoke Particle Impact Detector (SPID), newly designed at the University of Tromsø, was launched from Andøya 09:13 UTC the 13. January 2019. SPID is designed to detect meteoric smoke particles (MSPs) in winter mesospheric conditions. The rocket had a velocity of 1600 ms-1 at ~55 km where the nosecone was separated. At ~ 60km, SPID detected a signal of 17nA on the middle plate. The dynamics of the particles entering the detector was investigated taking into account the drag of the neutral airflow as well as the electric field generated by the bias voltages of the detector. These conditions were applied to a model of the size and charge of mesospheric dust in the range of radii 0.5 to 8 nm. For this model of the meteoric dust we find that 97 percent of particles that the rocket encounters would reach the middle plate and that 30 percent of the particles would hit the middle plate directly at 60 km. Estimations of dust densities that could explain the measured current vary between 10^10 and 101^3 per m^-3. The density of positive ions is close to that of MSPs, and so it is also possible that the measured current, or a fraction of it, is caused by ions. A secondary goal of the campaign was to investigate the relation between MSPs and the winter radar echoes called Polar Mesospheric Winter Echoes(PMWE). For this, the background atmospheric conditions were monitored with the radar systems MAARSY (53.5 MHz) and EISCAT (224 MHz). The EISCAT measured incoherent scatter which showed weak precipitation above 85 km. MAARSY did not observe PMWE activity during the launch, but on the days prior and after launch. Because it is a prerequisite to observe PMWE that the electron density is sufficiently high, we cannot draw any conclusions on the link between PMWE and MSP from the presented observations. The spectral analysis of the measured current shows strong rotational effects at higher altitudes. The Power spectrum follows the Kolmogorov slope of k^-5/3 into the Bragg scale of MAARSY, suggesting turbulent conditions influence the current. Because the resolution of the SPID is close to the Bragg scales of MAARSY, no clear conclusion could be made for the Bragg scale turbulence conditions

Solar wind magnetic holes can cross the bow shock and enter the magnetosheath

Solar wind magnetic holes are localized depressions of the magnetic field strength, on timescales of seconds to minutes. We use Cluster multipoint measurements to identify 26 magnetic holes which are observed just upstream of the bow shock and, a short time later, downstream in the magnetosheath, thus showing that they can penetrate the bow shock and enter the magnetosheath. For two magnetic holes, we show that the relation between upstream and downstream properties of the magnetic holes are well described by the MHD (magnetohydrodynamic) Rankine&ndash;Hugoniot (RH) jump conditions. We also present a small statistical investigation of the correlation between upstream and downstream observations of some properties of the magnetic holes. The temporal scale size and magnetic field rotation across the magnetic holes are very similar for the upstream and downstream observations, while the depth of the magnetic holes varies more. The results are consistent with the interpretation that magnetic holes in Earth's and Mercury's magnetosheath are of solar wind origin, as has previously been suggested. Since the solar wind magnetic holes can enter the magnetosheath, they may also interact with the magnetopause, representing a new type of localized solar wind&ndash;magnetosphere interaction. &nbsp;</p

Downstream high-speed plasma jet generation as a direct consequence of shock reformation

Shocks are one of nature's most powerful particle accelerators and have been connected to relativistic electron acceleration and cosmic rays. Upstream shock observations include wave generation, wave-particle interactions and magnetic compressive structures, while at the shock and downstream, particle acceleration, magnetic reconnection and plasma jets can be observed. Here, using Magnetospheric Multiscale (MMS) we show in-situ evidence of high-speed downstream flows (jets) generated at the Earth's bow shock as a direct consequence of shock reformation. Jets are observed downstream due to a combined effect of upstream plasma wave evolution and an ongoing reformation cycle of the bow shock. This generation process can also be applicable to planetary and astrophysical plasmas where collisionless shocks are commonly found. Several mechanisms exist for formation of jets observed in Earth's magnetosheath. Here, the authors show evidence of high-speed downstream flows generated at the Earth's bow shock as a direct consequence of shock reformation, which is different than the proposed mechanisms.Peer reviewe

CHARGING AND DETECTION OF MESOSPHERIC DUST WITH INSTRUMENT SPID ON G-CHASER ROCKET

The Smoke Particle Impact Detector (SPID) was flown on the G-Chaser student rocket that was launched from Andøya on 13 January 2019. SPID is a Faraday cup instrument with applied bias voltages to deflect the ambient plasma and a target area inside the probe designed to measure the dust particles by charge detection. The charging process of the dust particles in the detector is important for interpretation of the measurements and the influence of the charging models is discussed. Preliminary analysis of the SPID observations shows that ambient plasma and sunlight had an influence on the signals; further analysis is needed to retrieve information on impacting dust from the data

On the Meteoric Smoke Particle Detector SPID: Measurements and analysis from the G-chaser rocket campaign

The Smoke Particle Impact Detector (SPID), newly designed at the University of Tromsø, was launched from Andøya 09:13 UTC the 13. January 2019. SPID is designed to detect meteoric smoke particles (MSPs) in winter mesospheric conditions. The rocket had a velocity of 1600 ms-1 at ~55 km where the nosecone was separated. At ~ 60km, SPID detected a signal of 17nA on the middle plate. The dynamics of the particles entering the detector was investigated taking into account the drag of the neutral airflow as well as the electric field generated by the bias voltages of the detector. These conditions were applied to a model of the size and charge of mesospheric dust in the range of radii 0.5 to 8 nm. For this model of the meteoric dust we find that 97 percent of particles that the rocket encounters would reach the middle plate and that 30 percent of the particles would hit the middle plate directly at 60 km. Estimations of dust densities that could explain the measured current vary between 10^10 and 101^3 per m^-3. The density of positive ions is close to that of MSPs, and so it is also possible that the measured current, or a fraction of it, is caused by ions. A secondary goal of the campaign was to investigate the relation between MSPs and the winter radar echoes called Polar Mesospheric Winter Echoes(PMWE). For this, the background atmospheric conditions were monitored with the radar systems MAARSY (53.5 MHz) and EISCAT (224 MHz). The EISCAT measured incoherent scatter which showed weak precipitation above 85 km. MAARSY did not observe PMWE activity during the launch, but on the days prior and after launch. Because it is a prerequisite to observe PMWE that the electron density is sufficiently high, we cannot draw any conclusions on the link between PMWE and MSP from the presented observations. The spectral analysis of the measured current shows strong rotational effects at higher altitudes. The Power spectrum follows the Kolmogorov slope of k^-5/3 into the Bragg scale of MAARSY, suggesting turbulent conditions influence the current. Because the resolution of the SPID is close to the Bragg scales of MAARSY, no clear conclusion could be made for the Bragg scale turbulence conditions

On magnetosheath jet kinetic structure and plasma properties

High-speed plasma jets downstream of Earth's bow shock are high velocity streams associated with a variety of shock and magnetospheric phenomena. In this work, using the Magnetosphere Multiscale mission, we study the properties of a jet found downstream of the Quasi-parallel bow shock using high-resolution (burst) data. By doing so, we demonstrate how the jet is an inherently kinetic structure described by highly variable velocity distributions. The observed distributions show the presence of two plasma population, a cold/fast jet and a hotter/slower background population. We derive partial moments for the jet population to isolate its properties. The resulting partial moments appear different from the full ones which are typically used in similar studies. These discrepancies show how jets are more similar to upstream solar wind beams compared to what was previously believed. Finally, we explore the consequences of our results and methodology regarding the characterization, origin, and evolution of jets

High-speed Downstream Plasma Jet Generated due to Shock Reformation

Magnetosheath jets are transient, localized dynamic pressure enhancements found behind Earth’s bow shock. They have been associated to a variety of phenomena and effects, including, magnetopause reconnection, excitation of ULF waves and direct plasma penetration in the magnetosphere. While the have been observed for several decades, their origin is not yet fully understood. In this work, we use Magnetosphere Mutliscale (MMS) measurement to show the generation of a high-speed downstream jet resulting from the shock reformation process. The jet appears to be associated to the evolution of the upstream waves found upstream of a Short Large Amplitude Magnetic Structure (SLAMS). As the initial SLAMS eventually continues to form the magnetosheath region, a newly formed foreshock magnetic structure appears, acting as the local bow shock front. This process allows the solar wind to be effectively found downstream of the new local shock front, forming a magnetosheath jet. The limited interaction of the solar wind with the old shock (initial SLAMS) allow the slightly compressed solar wind to retain its initial high velocity, which correspond to a plasma jet relatively to the background. The formation mechanism, we show, does not require any external solar wind related transient phenomena to occur and could provide an answer on how jets could form in situations where strong rippling is not observed in the quasi-parallel bow shock

CHARGING AND DETECTION OF MESOSPHERIC DUST WITH INSTRUMENT SPID ON G-CHASER ROCKET

The Smoke Particle Impact Detector (SPID) was flown on the G-Chaser student rocket that was launched from Andøya on 13 January 2019. SPID is a Faraday cup instrument with applied bias voltages to deflect the ambient plasma and a target area inside the probe designed to measure the dust particles by charge detection. The charging process of the dust particles in the detector is important for interpretation of the measurements and the influence of the charging models is discussed. Preliminary analysis of the SPID observations shows that ambient plasma and sunlight had an influence on the signals; further analysis is needed to retrieve information on impacting dust from the data

Observation of mesospheric dust and ionospheric conditions during the G-chaser rocket campaign

Paper at 24th ESA Symposium on European Rocket and Balloon Programmes and Related Research, Essen, Germany, 16-20 June 2019. Conference home page.SPID, Smoke Particle Impact Detector, is a Faraday cup detector designed to measure nanometer-sized meteoric smoke particles during rocket flights. We report measurements made with SPID during the G-Chaser student rocket campaign 13 January 2019 and describe the design of the SPID instruments. Model calculations of dust trajectories within the detector result in an effective crosssection of 0.97 for particles larger than 0.5 nm at 60 km. Data analysis indicates that in order to generate the measured current, the number densities must be ∼ 1010m−3 or higher at 60 km. During the campaign the ground systems MAARSY and EISCAT were operating. These ground measurements showed smooth ionospheric conditions with weak precipitation down to 90 km. As a secondary goal of the campaign we wanted to investigate the possible connection between PMWE and MSPs. On the day of the launch there was no sign of PMWE and no conclusions can be drawn at this point

Observation of mesospheric dust and ionospheric conditions during the G-chaser rocket campaign

SPID, Smoke Particle Impact Detector, is a Faraday cup detector designed to measure nanometer-sized meteoric smoke particles during rocket flights. We report measurements made with SPID during the G-Chaser student rocket campaign 13 January 2019 and describe the design of the SPID instruments. Model calculations of dust trajectories within the detector result in an effective crosssection of 0.97 for particles larger than 0.5 nm at 60 km. Data analysis indicates that in order to generate the measured current, the number densities must be ∼ 1010m−3 or higher at 60 km. During the campaign the ground systems MAARSY and EISCAT were operating. These ground measurements showed smooth ionospheric conditions with weak precipitation down to 90 km. As a secondary goal of the campaign we wanted to investigate the possible connection between PMWE and MSPs. On the day of the launch there was no sign of PMWE and no conclusions can be drawn at this point