Maximum Occurrence Rate Research Articles

Eta-Earth Revisited I: A Formula for Estimating the Maximum Number of Earth-Like Habitats.

In this hypothesis article, we discuss the basic requirements of planetary environments where aerobe organisms can grow and survive, including atmospheric limitations of millimeter-to-meter-sized biological animal life based on physical limits and O2, N2, and CO2 toxicity levels. By assuming that animal-like extraterrestrial organisms adhere to similar limits, we define Earth-like habitats (EH) as rocky exoplanets in the habitable zone for complex life that host N2-O2-dominated atmospheres with minor amounts of CO2, at which advanced animal-like life or potentially even extraterrestrial intelligent life can in principle evolve and exist. We then derive a new formula that can be used to estimate the maximum occurrence rate of such Earth-like habitats in the Galaxy. This contains realistic probabilistic arguments that can be fine-tuned and constrained by atmospheric characterization with future space and ground-based telescopes. As an example, we briefly discuss two specific requirements feeding into our new formula that, although not quantifiable at present, will become scientifically quantifiable in the upcoming decades due to future observations of exoplanets and their atmospheres. Key Words: Eta-Earth-Earth-like habitats-oxygenation time-nitrogen atmospheres-carbon dioxide-animal-like life. Astrobiology 24, 897-915.

Statistical Characteristics of Spread F in the Northeastern Edge of the Qinghai-Tibet Plateau during 2017–2022

Spread F (SF) in the ionosphere can be observed frequently in mid-latitude regions. It is suggested that atmospheric gravity waves play a significant role for the seeding of mid-latitude SF. Previous research suggested that the source of travelling ionospheric disturbances (TIDs) over China is in the southeastern and northeastern edge of the Qinghai-Tibet Plateau, however, until now there have been no ground-based observations of the ionosphere in this region. Recently, an advanced digital ionosonde was installed at Zhangye station (39.2°N, 100.54°E, Dip Lat 29.6°N) in the northeastern edge of the Qinghai-Tibet Plateau. It is an opportunity to verify the effect of gravity waves on the formation of mid-latitude SF by comparing it with observations in other regions of the Chinese sector. In this study, statistical analysis of SF recorded at Zhangye station during 2017–2022 was carried out. Results show that diurnal, seasonal and solar cycle characteristics of the occurrence rate of SF are similar with previous studies. At Zhangye station, the maximum occurrence rate of SF is during the post-midnight period in summer and winter. The occurrence rate of SF events have a negative relationship with solar activity. There is no obvious relationship between the occurrence rate of SF and geomagnetic activity. Comparing observations of other stations in the mid-latitude region, we found that the occurrence rates of SF (the annual maximum rates are from 33.83% to 53.29%) are much higher at Zhangye station. Further studies show that ionospheric disturbances can be observed frequently at Zhangye station, especially in autumn and winter. Gravity waves/TIDs in the northeast of the Qinghai-Tibet Plateau are suggested to explain the abnormal higher occurrence rate of SF at Zhangye station.

Selenium Deficiency Promotes Dilatation of the Aorta by Increasing Expression and Activity of Vascular Smooth Muscle Cell Derived Matrix Metalloproteinase-2

Selenium (Se) is a key part of the body's oxidation defence system. However, it is unclear whether Se affects the development of aortic aneurysm (AA). An animal experiment was conducted to clarify the role of Se in AA development. C57BL/6N male mice were fed with a Se deficient (Se-D, < 0.05 mg/kg), Se adequate (Se-A, 0.2 mg/kg), or Se supplemented (Se-S, 1 mg/kg) diet for 8 weeks. Subsequently, an AA murine model (Se-D, n= 11; Se-A, n= 12; Se-S, n= 15) was established using angiotensin II (Ang II, 1 mg/kg/min) for four weeks plus β-aminopropionitrile (BAPN, 1 mg/mL) for the first two weeks. Saline replaced Ang II, and BAPN was removed during the modelling process for sham mice (Se-A, n= 9). To determine whether Se deficiency promoted aortic dilation via matrix metalloproteinase-2 (MMP-2), the non-specific MMP inhibitor doxycycline (Dox, 100 mg/kg/day) was given to Se-D AA mice (n= 7) for two weeks. The maximum aortic diameter in Se-D AA model mice was significantly increased compared with Se-A AA model mice. MMP-2 expression and activity in the aortic media of Se-D AA model mice was significantly increased compared with Se-A AA model mice. A large number of vascular smooth muscle cells (VSMCs) were found aggregating in the media of the non-dilated aorta of Se-D AA model mice, which was completely inhibited by Dox. The percentage of VSMCs in aortic media of Se-D AA model mice was significantly higher than in Se-A AA model mice. The maximum aortic diameter and occurrence rate of AA in Se-D AA model mice with Dox were significantly reduced compared with Se-D AA model mice. Se deficiency promoted dilatation of the aorta in AA model mice by increasing expression and activity of VSMC derived MMP-2, causing abnormal aggregation and proliferation of VSMCs in aortic media.

A statistical study of space hurricanes in the Northern Hemisphere

The space hurricane is a newly discovered large-scale three-dimensional magnetic vortex structure that spans the polar ionosphere and magnetosphere. At the height of the ionosphere, it has a strong circular horizontal plasma flow with a nearly zero-flow center and a coincident cyclone-shaped aurora caused by strong electron precipitation associated with intense upward magnetic field-aligned currents. By analyzing the long-term optical observation onboard the Defense Meteorological Satellite Program (DMSP) F16 satellite from 2005 to 2016, we found that space hurricanes in the Northern Hemisphere occur in summer and have a maximum occurrence rate in the afternoon sector around solar maximum. In particular, space hurricanes are more likely to occur in the dayside polar cap at magnetic latitudes greater than 80°, and their MLT (magnetic local time) dependence shows a positive relationship with the IMF (interplanetary magnetic field) clock angle. We also found that space hurricanes occur mainly under dominant positive IMF By and Bz and negative Bx conditions. It is suggested that the stable high-latitude lobe reconnection, which occurs under the conditions of a large Earth’s dipole tilt angle and high ionosphere conductivity in summer, should be the formation mechanism of space hurricanes. The result will give a better understanding of the solar wind–magnetosphere–ionosphere coupling process under northward IMF conditions.

Statistical Analysis of the Spatiotemporal Distribution of Lower Atmospheric Ducts over the Seas Adjacent to China, Based on the ECMWF Reanalysis Dataset

On the basis of 12 years of the European Centre for Mesoscale Weather Forecasts (ECMWF) reanalysis dataset, we statistically analyzed the spatiotemporal distribution of lower atmospheric ducts over the seas around China, and we investigated the possible generation mechanisms. The results show that the ducts’ occurrence had obvious seasonal and regional variations. Ducting events were more likely to occur in spring and summer, and the maximum occurrence rate reached 45.6%, which was closely related to the East Asian monsoon. The ducts’ altitude in continental coastal areas was lower than that far from the coast due to the dominance of surface ducts. The ducts’ thickness varied between 50 m and 450 m, and the thicker ducts were mainly concentrated in the South China Sea and the Pacific Ocean on the east side of the East China Sea near the Philippines and Taiwan. Except for a few areas, the ducts’ intensity was less than 10 M-units (an M-unit is the unit of atmospheric modified refractivity) and the diurnal variations were less pronounced. The duct formation in the lower atmosphere was related to factors such as monsoons, tropical cyclones, ocean currents, radiative cooling, and sea–land breezes.

Small‐Scale Magnetic Holes in the Solar Wind Observed by Parker Solar Probe

AbstractThe small‐scale magnetic hole (SSMH), characterized by magnetic field depression, is a structure with the size in the order of proton gyro‐radius. SSMHs near the Earth or other planets have been widely observed in recent years. However, SSMHs in the solar wind near the Sun are rarely investigated due to mission constraints. In the present study, SSMHs in the pristine solar wind within a wide heliocentric distance range are analyzed based on the Parker Solar Probe (PSP) Mission measurements. A total of 2,416 SSMHs are successfully identified during the orbits of PSP from 2nd October, 2018, to 31st December, 2020, with an average occurrence rate of ∼5.8 events/day. The occurrence rate of SSMHs decreases from ∼29.5 to ∼0.6 events/day as the heliocentric distance R increases. The spatial scale of these SSMHs obeys a bi‐log‐normal distribution, with the median scale L ∼ 137 km (∼6 ρp, proton gyro‐radius). As interplanetary magnetic field Bave increases or R decreases, the upper limit of the spatial scale L corresponding to each bin extends to a larger value. The L corresponding to the maximum occurrence rate also increases when Bave increases and R decreases. Besides, the SSMHs tend to occur more frequently in the solar wind environment with weak Bave and high thermal pressure Pt. Our results shed light on the characteristics and the origin of SSMHs in the pristine solar wind.

Solar Cycle and Seasonal Variability of Martian Ionospheric Irregularities from Mars Atmosphere and Volatile Evolution Observations

Spacecraft observations around Mars show that ionospheric irregularities occur frequently in the Martian ionosphere. In this study, Mars Atmosphere and Volatile Evolution data (the region is below ∼200 km) during 2015 January to 2021 March were used to revisit the statistical characteristics of ionospheric irregularities and the comparison of irregularities in Martian years with higher or lower solar activity phase of solar cycle. Results show that the characteristics of the irregularities with a larger length scale associated with the magnetic field and solar zenith angle are similar to the previous studies. Moreover, our results show that the occurrence rate of irregularities exhibits dawn and dusk asymmetry, and the occurrence rate at dusk is higher than that at dawn. In addition, results demonstrate that the occurrence rate of irregularities is higher in Martian years with higher solar activity than Martian years with lower solar activity, which means that the solar cycle might play an important role in the formation of irregularity events. Further studies show that the solar zenith angle (SZA) and altitude at the maximum occurrence rate depend on the level of solar activity. The SZA and altitude of the maximum occurrence rate are smaller in the Martian year with higher solar activity than the lower. We also found that the rate of events is lower during the day than the terminator in the ionospheric dynamo region. By contrast, in the regions where both electrons and ions are magnetized, events have a higher rate during the day than the terminator. Furthermore, the seasonal variation of the irregularity events was also presented in this study. Results show that the occurrence rate in the dynamo region with 80° < SZA < 150° in MY34 and MY35 show an incremental trend from spring to winter, but this trend is not obvious in MY33.

A statistical study on the occurrence characteristics of low-to-midlatitude ionospheric density enhancements (plasma blobs)

A statistical study on the occurrence characteristics of global low-to-midlatitude topside ionospheric density enhancements (plasma blobs) has been carried out using the ROCSAT-1 (Republic of China Satellite-1) data during high solar activity period of 1999 to 2004. The latitudinal distribution of plasma blobs indicates that the occurrence rates increase from the dip latitude ±15° to midlatitudes that appear to complement the latitudinal distribution of equatorial plasma bubbles (EPBs). For the seasonal distribution, it is found that the maximum occurrence rate appears during the June solstice in both northern and southern hemispheres. The local-time distribution indicates a maximum occurrence rate around midnight, and maintains a high occurrence rate until about 04 h in local time in contrast to a rapid decrease after midnight for the EPB occurrences. Negative correlation with the solar activity is found for the occurrence of plasma blobs that is opposite to the positive correlation with the solar activity for the EPB occurrences. All these different and contrasting occurrence characteristics between the low-to-midlatitude plasma blob occurrence and the EPBs imply that the occurrence mechanism for the low-to-midlatitude plasma blobs should have little relationship to that of EPBs. From the fact that an upward/outward plasma drift and the increase of O+ species are observed inside the plasma blob, an eastward polarization electric field should directly appear at topside ionosphere for the occurrence of plasma blobs. This polarization electric field should be mapped from the nighttime midlatitude Es layer instability process where the polarization electric field is generated.

The frequency of extreme X-ray variability for radio-quiet quasars

ABSTRACT We analyse 1598 serendipitous Chandra X-ray observations of 462 radio-quiet quasars to constrain the frequency of extreme amplitude X-ray variability that is intrinsic to the quasar corona and innermost accretion flow. The quasars in this investigation are all spectroscopically confirmed, optically bright (mi ≤ 20.2), and contain no identifiable broad absorption lines in their optical/ultraviolet spectra. This sample includes quasars spanning z ≈ 0.1–4 and probes X-ray variability on time-scales of up to ≈12 rest-frame years. Variability amplitudes are computed between every epoch of observation for each quasar and are analysed as a function of time-scale and luminosity. The tail-heavy distributions of variability amplitudes at all time-scales indicate that extreme X-ray variations are driven by an additional physical mechanism and not just typical random fluctuations of the coronal emission. Similarly, extreme X-ray variations of low-luminosity quasars seem to be driven by an additional physical mechanism, whereas high-luminosity quasars seem more consistent with random fluctuations. The amplitude at which an X-ray variability event can be considered extreme is quantified for different time-scales and luminosities. Extreme X-ray variations occur more frequently at long time-scales (Δt ≳ 300 d) than at shorter time-scales and in low-luminosity quasars compared to high-luminosity quasars over a similar time-scale. A binomial analysis indicates that extreme intrinsic X-ray variations are rare, with a maximum occurrence rate of $\lt 2.4{{\ \rm per\ cent}}$ of observations. Finally, we present X-ray variability and basic optical emission-line properties of three archival quasars that have been newly discovered to exhibit extreme X-ray variability.

Ionospheric F Layer Scintillation Weakening as Observed by COSMIC/FORMOSAT‐3 During the Major Sudden Stratospheric Warming in January 2013

AbstractSudden stratospheric warming (SSW) events in Northern Hemisphere winter atmosphere play a significant effect on large ionospheric disturbances. Nevertheless, the SSW effects on small‐scale structure in ionosphere, that is, the ionospheric F layer irregularities, are generally lack of understanding. This work carefully studied the equatorial F layer scintillation during the SSW event extending from 4 January to 5 February in 2013 by using the data of COSMIC/FORMOSAT‐3 (a Constellation Observing System for Meteorology, Ionosphere, and Climate mission). The occurrence rate of ionospheric F layer scintillation was found to be apparently decreased by about 30% during the SSW period. This phenomenon was obviously seen in American sector (90°W–0°) and African sector (0°–90°E). Another prominent feature was the ~0.5 local time hour delay of maximum scintillation occurrence rate associated with the suppression of equatorial F layer irregularities in the first 2 hr after the sunset during the SSW event in January 2013.

Statistical Analysis of Equatorial Plasma Irregularities Retrieved From Swarm 2013–2019 Observations

AbstractIn this study, we present a statistical analysis of equatorial plasma irregularities (EPIs) by using in situ plasma density measurements of the Swarm constellation from December 2013 to December 2019. The occurrence patterns for both postsunset and postmidnight EPIs with respect to longitude, season, local time, latitude, solar activity, and geomagnetic activity level are investigated. The main findings are as follows: (1) The postsunset/postmidnight EPIs occurrence rates exhibit different longitudinal and seasonal dependence: The postsunset EPIs have the maximum occurrence rate over the American‐Atlantic sectors during the December solstice and equinoxes, and the postmidnight EPIs have the maximum occurrence rate during the June solstice, especially over the African sector. (2) The postsunset EPIs occurrence rates have a positive correlation with solar activity, while the postmidnight EPIs are negatively correlated with it. (3) The latitudinal distribution of EPIs exhibits a double‐peak structure around ±5° magnetic latitude with a more significant peak in the summer hemisphere. (4) The EPIs occurrence rate increases with increasing geomagnetic activity level. (5) The main controlling factors for the distribution of postsunset EPIs are the magnetic declination angle, equatorial vertical E × B drift, and thermospheric zonal wind. For the postmidnight EPIs, the main controlling factors are likely to be atmospheric gravity waves and equatorward thermospheric meridional wind associated with midnight temperature maximum.

Properties of Localized Precipitation of Energetic Protons Equatorward of the Isotropic Boundary

AbstractUsing National Oceanic and Atmospheric Administration Polar Orbiting Environmental Satellite (NOAA/POES) observations of energetic protons, we for the first time investigated statistical properties of a specific type of particle precipitation—localized precipitation of energetic protons (LPEP) equatorward of the isotropy boundary. The maximum occurrence rate was found in the day‐afternoon sector at L &gt; 6. The maximum precipitating flux is found at lower L shells (L = 4–5). The dependence of LPEP occurrence and intensity on the geomagnetic activity indices and solar wind parameters is investigated. In particular, while the precipitating proton flux increases with geomagnetic activity everywhere, the occurrence rate in the day‐afternoon sector at L &gt; 6 decreases under the strongest activity. We conclude that revealed LPEP properties are mostly similar to those obtained for electromagnetic ion cyclotron waves on the basis of data from previous spacecraft missions. This similarity supports the suggestion on LPEP as the result of ion cyclotron instability in the magnetosphere.

Detections and constraints on white dwarf variability from time-series GALEX observations

Abstract We search for photometric variability in more than 23 000 known and candidate white dwarfs (WDs), the largest ultraviolet survey compiled for a single study of WDs. We use gphoton, a publicly available calibration/reduction pipeline, to generate time-series photometry of WDs observed by GALEX. By implementing a system of weighted metrics, we select sources with variability due to pulsations and eclipses. Although GALEX observations have short baselines (≤30 min), we identify intrinsic variability in sources as faint as Gaia G = 20 mag. With our ranking algorithm, we identify 48 new variable WDs in archival GALEX observations. We detect 40 new pulsators: 36 have hydrogen-dominated atmospheres (DAVs), including one possible massive DAV, and four are helium-dominated pulsators (DBVs). We also detect eight new eclipsing systems; five are new discoveries, and three were previously known spectroscopic binaries. We perform synthetic injections of the light curve of WD 1145+017, a system with known transiting debris, to test our ability to recover similar systems. We find that the 3σ maximum occurrence rate of WD 1145+017-like transiting objects is $\le 0.5{{\ \rm per\ cent}}$.

Daytime Periodic Wave‐like Structures in the Ionosphere Observed at Low Latitudes over the Asian‐Australian Sector Using Total Electron Content from Beidou Geostationary Satellites

AbstractDaytime periodic wave‐like structures are statistically analyzed for the first time in the low‐latitude ionosphere over the Asian‐Australian sector using total electron content from Beidou geostationary satellites during 2016–2017. These structures have periods of about 18–28 min, which frequently occur during 11:00–17:00 local time in the winter at latitudes ranging between 17 and 25°N (10–18°N magnetic latitude [MLAT]) in the Northern Hemisphere, where they have a maximum occurrence rate of 80% at ~21°N (14°N MLAT). In the Southern Hemisphere, daytime periodic wave‐like structures are also observed during 11:00–15:00 local time in the winter within latitudes ranging between 6.0 and 11.1°S (15.4–21.6°S MLAT), although the peak occurrence rate is only approximately 40%. Compared with stratospheric gravity waves (GWs), the seasonal and latitudinal variations of daytime periodic wave‐like structures are generally consistent with those of stratospheric GWs. This gives a possible argument that daytime periodic wave‐like structures in the low‐latitude ionosphere could be generated in the low‐latitude ionosphere and triggered by GWs from the lower atmosphere.

Occurrence of EMIC waves and plasmaspheric plasmas derived from THEMIS observations in the outer magnetosphere: Revisit

AbstractWe have statistically studied the relationship between electromagnetic ion cyclotron (EMIC) waves and cold plasmaspheric plasma (Nsp) in the L range of 6–12 using the Time History of Events and Macroscale Interactions during Substorms (THEMIS) data for 2008–2011. The important observational results are as follows: (1) Under quiet geomagnetic conditions (Kp ≤ 1), the maximum occurrence rate of the hydrogen (H) band EMIC waves appears in the early morning sector (0600–0900 MLT) at the outermost region (L= 10–12). (2) Under moderate and disturbed conditions (Kp ≥ 2), the H‐band occurrence rate is higher in the morning‐to‐early‐afternoon sector for L &gt; 10. (3) The high‐occurrence region of helium (He) band waves for Kp ≤ 1 varies from L = 7 to 12 in radial distances along the local time (i.e., at L ∼ 7 near noon and at L= 8–12 near late afternoon). (4) The He‐band waves for Kp ≥ 2 are mainly localized between 1200 and 1800 MLT with a peak around 1500–1600 MLT at L= 8–10. (5) Nsp is much higher for the He‐band intervals than for the H‐band intervals by a factor of 10 or more. The He‐band high occurrence appears at a steep Nsp gradient region. (6) The morning‐afternoon asymmetry of the normalized frequency seen both in H‐band and He‐band is similar to the asymmetric distribution of Nsp along the local time. These observations indicate that the cold plasma density plays a significant role in determining the spectral properties of EMIC waves. We discuss whether a morning‐afternoon asymmetry of the EMIC wave properties can be explained by the spatial distribution of cold plasmaspheric plasma.

Statistical study of ELF/VLF emissions at subauroral latitudes in Athabasca, Canada

AbstractWe present the first statistical analysis of ELF/VLF emissions observed on the ground at subauroral latitudes that includes their features, occurrences, and association with solar wind and geomagnetic variations. Using a 100 kHz sampling loop antenna located in Athabasca, Canada (54.60°N, 246.36°E, L = 4.3), we monitored these emissions, including chorus, quasiperiodic emissions, and hiss, from November 2012 to October 2013. We found a maximum occurrence rate in the morning sector (06–07 MLT, magnetic local time) and a minimum in the night sector (∼18 to 02 MLT), in agreement with previous satellite measurements in the inner magnetosphere. We also found correlation between the ongoing substorm and storm activity and the increase of occurrence rates. The observed waves usually had a central frequency ∼1–3 kHz lower than the half‐gyrofrequency at the conjugate equatorial plane, indicating a wave source at higher latitudes. A superposed epoch analysis showed that the starting time of the ELF/VLF emissions is preceded by a rise in AE both on short (hours) and long (days) terms. Solar wind speed also started slowly rising ∼1.5 days before, while density and dynamic pressure decreased shortly afterward. This may signify that high‐speed solar wind conditions also contribute to the generation of ELF/VLF emissions detected at subauroral latitudes.

STATISTICAL STUDY OF IPDP EVENTS OBSERVED BY THE CARISMA NETWORK OF MAGNETOMETERS

AbstractDuring substorms energetic ions injected from the magnetotail plasma sheet could excite electromagnetic ion cyclotron (EMIC) waves in the inner magnetosphere. As a signature of EMIC waves, ground‐based magnetometers observed the Intervals of Pulsations of Diminishing Periods (IPDP). With the observations of the GOES satellite and CARISMA network of magnetometers in Canada, we analyzed the relationship between the IPDP events and substorm injection events. With the observations of magnetometers at MCMU and MSTK stations of CARISMA network between April 2005 and May 2014, we statistically analyzed the IPDP events during substorms and obtained the occurrence rate distribution in seasons and magnetic local time (MLT). A total of 128 IPDP events have been simultaneously observed by both MCMU and MSTK stations. The IPDP events have the least occurrence rate in winter (13.28%), and the highest occurrence rate in spring (32.81%). The results show that the occurrence rate of IPDP events is affected by the ionospheric conductivity and the occurrence rate of substorms. The maximum occurrence rate of the events is between 15 MLT and 18 MLT. Our result suggests that IPDP events are mainly generated by energetic anisotropic protons, which can be injected into the inner magnetosphere during substorms and drift westward and encounter the plasmaspheric plume.

Pc2-3 geomagnetic pulsations on the ground, in the ionosphere, and in the magnetosphere: MM100, CHAMP, and THEMIS observations

Abstract. We analyze Pc2-3 pulsations recorded by the CHAMP (CHAllenging Minisatellite Payload) satellite in the F layer of the Earth's ionosphere, on the ground, and in the magnetosphere during quiet geomagnetic conditions. The spectra of Pc2-3 pulsations recorded in the F layer are enriched with frequencies above 50 mHz in comparison to the ground Pc2-3 spectra. These frequencies are higher than the fundamental harmonics of the field line resonances in the magnetosphere. High quality signals with dominant frequencies 70–200 mHz are a regular phenomenon in the F layer and in the magnetosphere. The mean latitude of the maximum Pc2-3 occurrence rate lies at L &amp;amp;approx; 3.5 in the F layer, i.e., inside the plasmasphere. Day-to-day variations of the L value of the CHAMP Pc2-3 occurrence rate maximum follow the plasmapause day-to-day variations. Polarization and amplitude of Pc2-3s in the magnetosphere, in the ionosphere, and on the ground allow us to suggest that they are generated as fast magnetosonic (FMS) waves in the outer magnetosphere and are partly converted into shear Alfven waves near the plasmapause. The observed ground-to-ionosphere amplitude ratio during the night is interpreted as a result of the Alfven wave transmission through the ionosphere. The problem of wave transmission through the ionosphere is solved theoretically by means of a numerical solution of the full-wave equation for the Alfven wave reflection from and transmission through a horizontally stratified ionosphere. The best agreement between the calculated and measured values of the ground-to-ionosphere amplitude ratio is found for k = 5 × 10−3 km−1, i.e., the observed ground-to-ionosphere amplitude ratio corresponds to a wave spatial scale which could provide a Doppler shift within a few percent of the apparent frequency of the Pc2-3 pulsations as recorded by a low-orbiting spacecraft.

In-vitro Calcium Oxalate Crystallization Inhibition by Achyranthes aspera L. and Bryophyllum pinnatum Lam

Introduction: Urolithiasis has plagued human kind since antiquity and in the present era, its frequency is increasing with maximum occurrence rate of calcium oxalate stones. Although dramatic changes in the methods of its treatment has undertaken, still need exists for search of antilithic drugs from the nature. Thus, the inhibition of in-vitro calcium-oxalate crystal formation by Achyranthes aspera L. and Bryophyllum pinnatum Lam. was investigated. Methods: Leaf extracts of both the plants were screened by using nucleation assay. Different concentrations of both the extracts were screened. Results: In the nucleation assay the% inhibition for calcium oxalate crystal formation was found to be directly proportional to the increase in concentration of the plant extracts. Achyranthes aspera showed maximum inhibition of 60.06±0.19% at 1000 mg/ml while Bryophyllum pinnatum showed maximum inhibition of 49.93±0.07% at the same concentration. Conclusion: The present in-vitro study provides evidence that Achyranthes aspera is a potent anti-urolithiatic agent; however these in-vitro results should be confirmed in-vivo.

Solar wind electron precipitation into the dayside Martian upper atmosphere through the cusps of strong crustal fields

AbstractMeasurements made by the magnetometer/electron reflectometer on board the Mars Global Surveyor spacecraft have shown spatially localized enhancements in electron fluxes over the strong crustal fields on both the dayside and night, which are used to identify the cusps in between the closed magnetic fields. This paper provides a comprehensive statistical study on the occurrence rate of dayside solar wind/magnetosheath precipitation over the strong crustal fields. Also, the occurrence rate's dependence on the magnetic elevation angles and the solar zenith angle is presented. A seasonal variation of the precipitation is also expected and found, due to both the tilt and the orbital eccentricity of Mars. The maximum occurrence rate is 40%, when the solar zenith angles are small and the magnetic fields are nearly vertical. Finally, the energy flux deposition of the solar wind electrons is calculated as well, which is 0.1%–2% of solar EUV flux input.