The Earth's albedo is a fundamental climate parameter for understanding the radiation budget of the atmosphere. It has been traditionally measured not only from space platforms but also from the ...ground for 16 years from Big Bear Solar Observatory by observing the Moon. The photometric ratio of the dark (earthshine) to the bright (moonshine) sides of the Moon is used to determine nightly anomalies in the terrestrial albedo, with the aim of quantifying sustained monthly, annual, and/or decadal changes. We find two modest decadal scale cycles in the albedo, but with no significant net change over the 16 years of accumulated data. Within the evolution of the two cycles, we find periods of sustained annual increases, followed by comparable sustained decreases in albedo. The evolution of the earthshine albedo is in remarkable agreement with that from the Clouds and the Earth's Radiant Energy System instruments, although each method measures different slices of the Earth's Bond albedo.
Key Points
We presente a new 16 year long global albedo record (a fundamental climate parameter) taken using the earthshine methodolgy
The Earth's reflectance presents decadal variability, but overall no long‐term trend is identified
The new data seem to agree well with the only other available albedo data set, the one from CERES instrumentation
The Coudé feed of the vacuum telescope (aperture D = 65 cm) at the Big Bear Solar Observatory (BBSO) is currently completely remodelled to accommodate a correlation tracker and a high‐order Adaptive ...Optics (AO) system. The AO system serves two imaging magnetograph systems located at a new optical laboratory on the observatory's 2nd floor. The InfraRed Imaging Magnetograph (IRIM) is an innovative magnetograph system for near‐infrared (NIR) observations in the wavelength region from 1.0 μm to 1.6 μm. The Visible‐light Imaging Magnetograph (VIM) is basically a twin of IRIM for observations in the wavelength range from 550 nm to 700 nm. Both instruments were designed for high spatial and high temporal observations of the solar photosphere and chromosphere. Real‐time data processing is an integral part of the instruments and will enhance BBSO's capabilities in monitoring solar activity and predicting and forecasting space weather.
The Earth's albedo is a fundamental climate parameter for understanding the radiation budget of the atmosphere. It has been traditionally measured from space platforms, but also from the ground for ...sixteen years from Big Bear Solar Observatory by observing the Moon. The photometric ratio of the dark (earthshine) to the bright (moonshine) sides of the Moon is used to determine nightly anomalies in the terrestrial albedo, with the aim is of quantifying sustained monthly, annual and/or decadal changes. We find two modest decadal scale cycles in the albedo, but with no significant net change over the sixteen years of accumulated data. Within the evolution of the two cycles, we find periods of sustained annual increases, followed by comparable sustained decreases in albedo. The evolution of the earthshine albedo is in remarkable agreement with that from the CERES instruments, although each method measures different slices of the Earth's Bond albedo.
The New Solar Telescope (NST) is a 1.6-meter off-axis Gregory-type telescope with an equatorial mount and an open optical support structure. To mitigate the temperature fluctuations along the exposed ...optical path, the effects of local/dome-related seeing have to be minimized. To accomplish this, NST will be housed in a 5/8-sphere fiberglass dome that is outfitted with 14 active vents evenly spaced around its perimeter. The 14 vents house louvers that open and close independently of one another to regulate and direct the passage of air through the dome. In January 2006, 16 thermal probes were installed throughout the dome and the temperature distribution was measured. The measurements confirmed the existence of a strong thermal gradient on the order of 5 degree Celsius inside the dome. In December 2006, a second set of temperature measurements were made using different louver configurations. In this study, we present the results of these measurements along with their integration into the thermal control system (ThCS) and the overall telescope control system (TCS).
We present observations that provide the strongest evidence yet that discrete whistler mode chorus packets cause relativistic electron microbursts. On 20 January 2016 near 1944 UT the low Earth ...orbiting CubeSat Focused Investigations of Relativistic Electron Bursts: Intensity, Range, and Dynamics (FIREBIRD II) observed energetic microbursts (near L = 5.6 and MLT = 10.5) from its lower limit of 220 keV, to 1 MeV. In the outer radiation belt and magnetically conjugate, Van Allen Probe A observed rising‐tone, lower band chorus waves with durations and cadences similar to the microbursts. No other waves were observed. This is the first time that chorus and microbursts have been simultaneously observed with a separation smaller than a chorus packet. A majority of the microbursts do not have the energy dispersion expected for trapped electrons bouncing between mirror points. This confirms that the electrons are rapidly (nonlinearly) scattered into the loss cone by a coherent interaction with the large amplitude (up to ∼900 pT) chorus. Comparison of observed time‐averaged microburst flux and estimated total electron drift shell content at L = 5.6 indicate that microbursts may represent a significant source of energetic electron loss in the outer radiation belt.
Plain Language Summary
Relativistic microbursts are impulsive (<1 s), energetic (MeV) bursts of electrons precipitated from the magnetosphere into the atmosphere. They may constitute a major source of electron loss that helps bring the outer radiation belt back to quiet time levels following storm time enhancements. One possible cause of microbursts is scattering by a VLF plasma wave called chorus. However, simultaneous measurements of microbursts and chorus are extremely rare and this connection has not previously been directly shown. We provide the strongest evidence yet that chorus causes relativistic microbursts by comparing simultaneous observations from the Van Allen Probes and the Focused Investigations of Relativistic Electron Bursts: Intensity, Range, and Dynamics CubeSat. Results indicate that microbursts may indeed be an important source of energetic electron loss in the outer radiation belt.
Key Points
First published conjunction of simultaneous chorus and microbursts with a separation smaller than a chorus packet
Observations provide strongest evidence yet that chorus causes microbursts, from subrelativistic (200 keV) to relativistic (1 MeV) energies
The scattering is prompt and occurs off equator; it may be a significant source of relativistic electron loss in the outer belt
In this letter, we present the results of a conjunction between the Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) satellite and a Time History of Events and Macroscale Interactions ...during Substorms (THEMIS) all‐sky imager in Gillam, Canada, showing a high correlation between relativistic, >1 MeV, electron microbursts and a type of pulsating aurora called patchy aurora. The correlation was 0.8, and is not serendipitous. While the relationship between pulsating aurora and 10–100s keV microbursts has been previously predicted, here we show a strong association between keV and MeV electron dynamics, possibly spanning two orders of magnitude. Importantly, this result shows that the dynamics of relativistic radiation belt electrons are at times intimately tied to keV electron precipitation, and cannot be studied in isolation.
Plain Language Summary
In this letter, we present a coordinated observation between a low Earth orbiting satellite, orbiting at 400 km altitude above Earth's surface, and an auroral all‐sky imager in Canada. This observation showed a connection of a type of pulsating aurora, called patchy aurora, with extremely energetic and intense bursts of electron radiation called microbursts. This link is surprising because the electron energies responsible for auroral light are 100 times lower than the electrons that were directly observed in space. Our result implies that the mechanism responsible for patchy aurora and microbursts is likely the same, and could be capable of affecting electrons with vastly different energies. This result is a major step toward unifying the microburst and patchy aurora phenomena and shows that the dynamics of high‐energy electrons located in near‐Earth space can be intimately tied to much lower energy electron precipitation, and must therefore be studied together.
Key Points
We identified a conjunction between the low Earth orbiting Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) satellite and a Time History of Events and Macroscale Interactions during Substorms (THEMIS) all‐sky imager at Gillam, Canada
We found a high correlation between patchy aurora and >1 MeV electron microburst precipitation observed during the conjunction
This correlation suggests a close connection between relativistic electron microbursts and patchy aurora
Electromagnetic ion cyclotron (EMIC) waves are known to typically cause electron losses into Earth's upper atmosphere at >~1 MeV, while the minimum energy of electrons subject to efficient ...EMIC‐driven precipitation loss is unresolved. This letter reports electron precipitation from subrelativistic energies of ~250 keV up to ~1 MeV observed by the Focused Investigations of Relativistic Electron Burst Intensity, Range and Dynamics (FIREBIRD‐II) CubeSats, while two Polar Operational Environmental Satellites (POES) observed proton precipitation nearby. Van Allen Probe A detected EMIC waves (~0.7–2.0 nT) over the similar L shell extent of electron precipitation observed by FIREBIRD‐II, albeit with a ~1.6 magnetic local time (MLT) difference. Although plasmaspheric hiss and magnetosonic waves were also observed, quasi‐linear calculations indicate that EMIC waves were the most efficient in driving the electron precipitation. Quasi‐linear theory predicts efficient precipitation at >0.8–1 MeV (due to H‐band EMIC waves), suggesting that other mechanisms are required to explain the observed subrelativistic electron precipitation.
Plain Language Summary
Plasma waves in the Earth's magnetosphere can alter the trajectory of particles traveling along geomagnetic field lines. Specifically, electromagnetic ion cyclotron (EMIC) waves can interact with both electrons and protons and cause them to fall into the upper atmosphere of Earth. From past studies and theories, it is known that EMIC waves drive precipitation of ultrarelativistic (>~MeV) electrons and tens to hundreds of keV protons. Such electron precipitation can lead to atmospheric changes and potentially aid ozone depletion. In this work, we show a direct observation of electron precipitation from ~250 keV up to ~1 MeV, potentially driven by EMIC waves using multipoint measurements primarily from a CubeSat mission (FIREBIRD‐II) and Van Allen Probes. Quasi‐linear calculations indicate that EMIC waves are efficient in driving the electron precipitation at >0.8–1 MeV, but other mechanisms are needed to explain the observed electron precipitation down to ~250 keV. Our study also highlights the capabilities of FIREBIRD‐II studying not only microbursts, but also other precipitation patterns (e.g., driven by EMIC waves).
Key Points
Strong EMIC waves were observed by Van Allen Probe A in association with phase space density dips over the similar L shell extent
FIREBIRD‐II observed electron precipitation from ~250 keV up to ~1 MeV over the similar L shell extent of EMIC waves but at a later MLT
Quasi‐linear theory predicts efficient precipitation at > 0.8–1 MeV but requires other mechanisms to explain the subrelativistic one
Interactions between whistler mode chorus waves and electrons are a dominant mechanism for particle acceleration and loss in the outer radiation belt. One form of this loss is electron microburst ...precipitation: a sub‐second intense burst of electrons. Despite previous investigations, details regarding the microburst‐chorus scattering mechanism—such as dominant resonance harmonic—are largely unconstrained. One way to observationally probe this is via the time‐of‐flight energy dispersion. If a single cyclotron resonance is dominant, then higher energy electrons will resonate at higher magnetic latitudes: sometimes resulting in an inverse time‐of‐flight dispersion with lower‐energy electrons leading. Here we present a clear example of this phenomena, observed by a FIREBIRD‐II CubeSat on 27 August 2015, that shows good agreement with the Miyoshi‐Saito time‐of‐flight model. When constrained by this observation, the Miyoshi‐Saito model predicts that a relatively narrowband chorus wave with a ∼0.2 of the equatorial electron gyrofrequency scattered the microburst.
Plain Language Summary
Wave‐particle interactions are a ubiquitous phenomenon in plasmas. Around Earth, interactions between electrons and a plasma wave termed whistler mode chorus leads to both the acceleration of the outer Van Allen radiation belt electrons, and rapid precipitation of electrons into Earth's atmosphere. One form of this precipitation is called electron microbursts: a sub‐second and intense bursts of electrons most often observed by high altitude balloons and low Earth orbiting satellites. While microbursts have been studied since the dawn of the Space Age, fundamental details regarding how they are generated are largely unknown. One clue to the properties of the scattering mechanism comes from energy‐dependent time‐of‐flight dispersion signatures. Electrons with a larger kinetic energy move faster, and will therefore precipitate before the electrons with lower kinetic energy. However, in this paper we show observations made by the FIREBIRD‐II CubeSat mission of the opposite: lower‐energy electrons arriving first. This counter‐intuitive phenomena, termed inverse time‐of‐flight energy dispersion, together with models, is a powerful tool to sense the detailed nature of how plasma waves scatter electrons in Earth's near space environment.
Key Points
FIREBIRD‐II observed a microburst whose 250 keV electrons arrived before the 650 keV electrons
We estimate that the observed inverse energy dispersion of 0.1 ms/keV is statistically significant
Our observations are consistent with the inverse time‐of‐flight model of chorus waves resonating with 100s keV electrons
We have identified for the first time an energy‐time dispersion of precipitating electron flux in a pulsating aurora patch, ranging from 6.7 to 580 keV, through simultaneous in‐situ observations of ...sub‐relativistic electrons of microburst precipitations and lower‐energy electrons using the Loss through Auroral Microburst Pulsation sounding rocket launched from the Poker Flat Research Range in Alaska. Our observations reveal that precipitating electrons with energies of 180–320 keV were observed first, followed by 250–580 keV electrons 0–30 ms later, and finally, after 500–1,000 ms, 6.7–14.6 keV electrons were observed. The identified energy‐time dispersion is consistent with the theoretical estimation that the relativistic electron microbursts are a high‐energy tail of pulsating aurora electrons, which are caused by chorus waves propagating along the field line.
Plain Language Summary
Microbursts, which are bursts of high energy electrons, and pulsating auroras, which periodically blink and caused by the precipitation of low energy electrons, are observed in the Earth's polar ionosphere. The detection time differences of the electrons associated with microbursts and pulsating auroras were detected by a sounding rocket. A possible mechanism for the generation of these precipitations is the interaction of electrons with a particular type of wave, known as “chorus,” which propagates along geomagnetic lines. The observed energy‐time dispersion of the precipitating electrons is quantitatively consistent with theories of electron precipitation based on this interaction.
Key Points
A sounding rocket observed simultaneously precipitating sub‐relativistic electron microbursts and pulsating auroral electrons
250–580 keV electron precipitations were detected 0–30 ms after 180–320 keV electron precipitations in a single auroral patch
The energy dispersion of observed electrons is consistent with the theory that they are due to chorus waves propagating to higher latitudes
PDF
