Long‐term magnetometer data of Venus Express are analyzed for the occurrence of waves at the proton cyclotron frequency in the spacecraft frame in the upstream region of Venus, for conditions of ...rising solar activity. The data of two Venus years up to the time of highest sunspot number so far (1 Mar 2011 to 31 May 2012) are studied to reveal the properties of the waves and the interplanetary magnetic field (IMF) conditions under which they are observed. In general, waves generated by newborn protons from exospheric hydrogen are observed under quasi‐ (anti)parallel conditions of the IMF and the solar wind velocity, as is expected from theoretical models. The present study near solar maximum finds significantly more waves than a previous study for solar minimum, with an asymmetry in the wave occurrence, i.e., mainly under antiparallel conditions. The plasma data from the Analyzer of Space Plasmas and Energetic Atoms instrument aboard Venus Express enable analysis of the background solar wind conditions. The prevalence of waves for IMF in direction toward the Sun is related to the stronger southward tilt of the heliospheric current sheet for the rising phase of Solar Cycle 24, i.e., the “bashful ballerina” is responsible for asymmetric background solar wind conditions. The increase of the number of wave occurrences may be explained by a significant increase in the relative density of planetary protons with respect to the solar wind background. An exceptionally low solar wind proton density is observed during the rising phase of Solar Cycle 24. At the same time, higher EUV increases the ionization in the Venus exosphere, resulting in higher supply of energy from a higher number of newborn protons to the wave. We conclude that in addition to quasi‐ (anti)parallel conditions of the IMF and the solar wind velocity direction, the higher relative density of Venus exospheric protons with respect to the background solar wind proton density is the key parameter for the higher number of observable proton cyclotron waves near solar maximum.
Key Points
More upstream PCWs at Venus near solar maximum compared to solar minimum
Increase due to higher ratio of planetary to SW proton density
Asymmetry in IMF at PCWs due to tilt of heliospheric current sheet
Most pollinators are generalists and therefore are likely to transfer heterospecific pollen among co-flowering plants. Most work on the impacts of heterospecific pollen deposition on plant fecundity ...has utilized hand-pollination experiments in greenhouse settings, and we continue to know very little about the reproductive effects of heterospecific pollen in field settings.
We explored how patterns of naturally deposited heterospecific pollen relate to the reproductive output of Delphinium barbeyi, a common subalpine perennial herb in the Rocky Mountains (USA). We assessed a wide range of naturally occurring heterospecific pollen proportions and pollen load sizes, and linked stigmatic pollen deposition directly to seed set in individual carpels in the field.
We found that heterospecific pollen deposition in D. barbeyi is common, but typically found at low levels across stigmas collected in our sites. Neither conspecific nor heterospecific pollen deposition was related to carpel abortion. By contrast, we saw a significant positive relationship between conspecific pollen amount and viable seed production, as well as a significant negative interaction between the effects of conspecific pollen and heterospecific pollen amount, whereby the effect of conspecific pollen on viable seed production became weaker with greater heterospecific deposition on stigmas.
To our knowledge, this is the first demonstration of a relationship between heterospecific pollen and seed production in a field setting. In addition, it is the first report of an interaction between conspecific and heterospecific pollen quantities on seed production. These findings, taken with the results from other studies, suggest that greenhouse hand-pollination studies and field studies should be more tightly integrated in future work to better understand how heterospecific pollen transfer can be detrimental for plant reproduction.
The South Korean meteorological and environmental satellite GEO-KOMPSAT-2A (GK-2A) was launched into geostationary orbit at
128.2
∘
East on 4 December 2018. The space weather observation aboard GK-2A ...is performed by the Korea Space Environment Monitor. It consists of three particle detectors, a charging monitor and a four-sensor Service Oriented Spacecraft Magnetometer (SOSMAG).
The magnetometer design aims for avoiding strict magnetic cleanliness requirements for the hosting spacecraft and an automated on-board correction of the dynamic stray fields which are generated by the spacecraft. This is achieved through the use of two science grade fluxgate sensors on an approximately one meter long boom and two additional magnetoresistance sensors mounted within the spacecraft body.
This paper describes the instrument design, discusses the ground calibration methods and results, presents the post-launch correction and calibration achievements based on the data which were acquired during the first year in orbit and demonstrates the in-flight performance of SOSMAG with two science cases.
The dynamic stray fields from the GK-2A spacecraft, which was built without specific magnetic cleanliness considerations, are reduced up to a maximum factor of 35. The magnitude of the largest remnant field from an active spacecraft disturber is 2.0 nT. Due to a daily shadowing of the SOSMAG boom, sensor intrinsic offset oscillations with a periodicity up to 60 minutes and peak-to-peak values up to 5 nT remain in the corrected data product.
The comparison of the cleaned SOSMAG data with the Tsyganenko 2004 magnetic field model and the magnetic field data from the Magnetospheric Multiscale mission demonstrates that the offset error is less than the required 5 nT for all three components and that the drift of the offsets over 10 months is less than 7 nT.
Future work will include a further reduction of the remaining artefacts in the final data product with the focus on lessening the temperature driven sensor oscillations with an epoch based identification and correction.
The magnetometer instrument MPO-MAG on-board the Mercury Planetary Orbiter (MPO) of the BepiColombo mission en-route to Mercury is introduced, with its instrument design, its calibration and ...scientific targets. The instrument is comprised of two tri-axial fluxgate magnetometers mounted on a 2.9 m boom and are 0.8 m apart. They monitor the magnetic field with up to 128 Hz in a
±
2048
nT range. The MPO will be injected into an initial
480
×
1500
km polar orbit (2.3 h orbital period). At Mercury, we will map the planetary magnetic field and determine the dynamo generated field and constrain the secular variation. In this paper, we also discuss the effect of the instrument calibration on the ability to improve the knowledge on the internal field. Furthermore, the study of induced magnetic fields and field-aligned currents will help to constrain the interior structure in concert with other geophysical instruments. The orbit is also well-suited to study dynamical phenomena at the Hermean magnetopause and magnetospheric cusps. Together with its sister instrument Mio-MGF on-board the second satellite of the BepiColombo mission, the magnetometers at Mercury will study the reaction of the highly dynamic magnetosphere to changes in the solar wind. In the extreme case, the solar wind might even collapse the entire dayside magnetosphere. During cruise, MPO-MAG will contribute to studies of solar wind turbulence and transient phenomena.
Aim - identify neuroimaging characteristics associated with different post-stroke fatigue (PSF) domains within first 6 months after ischemic strokes. There were enrolled in the study 107 patients ...with acute ischemic strokes. General PSF and certain PSF domains (global, physical, mental, motivational, activity-related) were measured by multidimensional fatigue inventory-20 (MFI-20) scale at hospital stay, in 1, 3 and 6 months after stroke occurrence. Brain MRI studies included cerebral infarct localization, planimetric measurements of infarct volumes, measurement of brain atrophy indexes (bifrontal, bicaudate, cortical atrophy indexes, width of third ventricle) and evaluation of leukoaraiosis severity, according to Fazekas scale. In univariate logistic regression analysis infarcts volumes as well as brain atrophy indexes were not significantly associated with risk of any PSF domain at any time points within first 6 months after ischemic strokes. On the other hand, it had been found reliable associations between subcortical infarcts and increased risk of PSF domains which are related just to physical activity (physical PSF, activity-related PSF) in 1 month after stroke onset and later, as well as reliable associations between infratentorial infarcts and risk of global PSF domain in 3 months after stroke and later. Moreover, it have been revealed significant direct associations between severity of white matter lesions and risk of mental PSF in 3 months after stroke onset and later. Subcortical infarcts may be risk factors for development of physical PSF domain, infratentorial infarcts - risk factors for development of global PSF domain, leukoaraiosis extension - risk factor for development of mental PSF domain but not early than 1 month after stroke occurrence.
The noncollisional interaction between conducting obstacles and magnetized plasma winds can be found in different scenarios, from the interaction occurring between regions inside galaxy clusters to ...the interaction between the solar wind and Mars, Venus, and active comets, or even the interaction between Titan and the Saturnian magnetospheric flow. These objects generate, through several current systems, perturbations in the streaming magnetic field leading to its draping around the obstacle's effective conducting surface. Recent observational results suggest that several properties associated with magnetic field draping, such as the location of the polarity reversal layer of the induced magnetotail, are affected by variations in the conditions of the streaming magnetic field. To improve our understanding of these phenomena, we perform a characterization of several magnetic field draping signatures by analytically solving an ideal problem in which a perfectly conducting magnetized plasma (with frozen-in magnetic field conditions) flows around a spherical body for various orientations of the streaming magnetic field. In particular, we compute the shift of the inverse polarity reversal layer as the orientation of the background magnetic field is changed.
We present a study on the properties of electromagnetic plasma waves in the region upstream of the Martian bow shock, detected by the magnetometer and electron reflectometer (MAG / ER) onboard the ...Mars Global Surveyor (MGS) spacecraft during the period known as Science Phasing Orbits (SPO). The frequency of these waves, measured in the MGS reference frame (SC), is close to the local proton cyclotron frequency. Minimum variance analysis (MVA) shows that these ‘proton cyclotron frequency’ waves (PCWs) are characterized – in the SC frame – by a left-hand, elliptical polarization and propagate almost parallel to the background magnetic field. They also have a small degree of compressibility and an amplitude that decreases with the increase of the interplanetary magnetic field (IMF) cone angle and radial distance from the planet. The latter result supports the idea that the source of these waves is Mars. In addition, we find that these waves are not associated with the foreshock and their properties (ellipticity, degree of polarization, direction of propagation) do not depend on the IMF cone angle. Empirical evidence and theoretical approaches suggest that most of these observations correspond to the ion–ion right hand (RH) mode originating from the pick-up of ionized exospheric hydrogen. The left-hand (LH) mode might be present in cases where the IMF is almost perpendicular to the Solar Wind direction. PCWs occur in 62% of the time during SPO1 subphase, whereas occurrence drops to 8% during SPO2. Also, SPO1 PCWs preserve their characteristics for longer time periods and have greater degree of polarization and coherence than those in SPO2. We discuss these results in the context of possible changes in the pick-up conditions from SPO1 to SPO2, or steady, spatial inhomogeneities in the wave distribution. The lack of influence from the Solar Wind's convective electric field upon the location of PCWs indicates that, as suggested by recent theoretical results, there is no clear relation between the spatial distribution of PCWs and that of pick-up ions.
► We study the properties of the PCW's present upstream from Mars. ► We analyze the frequency, propagation and polarization properties of these waves. ► We show statistical analyses of their amplitude and spatial distribution. ► We perform a statistical analysis of the Solar Wind IMF cone angle associated with them. ► We study the implications of our results and compare with recent studies.
We report on the temporal variability of the occurrence of waves at the local proton cyclotron frequency upstream from the Martian bow shock from Mars Global Surveyor observations during the first ...aerobraking and science phasing orbit periods. Observations at high southern latitudes during minimum‐to‐mean solar activity show that the wave occurrence rate is significantly higher around perihelion/southern summer solstice than around the spring and autumn equinoxes. A similar trend is observed in the hydrogen (H) exospheric density profiles over the Martian dayside and South Pole obtained from a model including UV thermospheric heating effects. In spite of the complexity in the ion pickup and plasma wave generation and evolution processes, these results support the idea that variations in the occurrence of waves could be used to study the temporal evolution of the distant Martian H corona and its coupling with the thermosphere at altitudes currently inaccessible to direct measurements.
Key Points
The occurrence of upstream waves at Mars varies with time
Variabilities of exospheric hydrogen density and wave abundance are similar
Inferred exospheric variability could be due to solar UV forcing on thermosphere
Aim - analyze factors associated with certain time-based types of post-stroke fatigue (PSF) over the first year after stroke occurrence. There were examined patients consequently in definite time ...points after ischemic or hemorrhagic strokes: at hospital stay (234 patients), at 1 month (203), at 3 months (176), at 6 months (156), at 9 months (139) and at 12 months (128). PSF and certain PSF domains were measured by fatigue assessment scale and multidimensional fatigue inventory-20 scale. All PSF cases were divided as early PSF (presented only within the first month after stroke), persistent PSF (presented within the first post-stroke month and later) and late PSF (appeared only at three months observation or later). In univariate logistic regression analysis there were no any significant associations between risk of every time-based PSF types and majority of studied factors. On the other hand, Fazekas scale score was significantly associated with higher risk of persistence of global and mental PSF. Post-stroke functional disability, according to modified Rankin scale, was significantly associated with increased risk of global and physical PSF persistence. Mild cognitive impairments were associated with increased risk of global and mental PSF persistence. The presence of depressive signs at 1 month and 3 months after stroke was significantly associated with increased risk of late PSF (due to increased risk of various PSF components). Management of post-stroke functional abnormalities, mild cognitive impairments and depressive signs probably may be helpful for prevention of early PSF persistence and development of late PSF.
Post-stroke fatigue (PSF) is a common and often debilitating sequel of both ischemic and hemorrhagic strokes Aim - identify socio-demographic, personal and psychological factors associated with ...different PSF domains over the second half year after stroke occurrence. There were examined patients consequently in definite time points: at 6 months (156 patients), at 9 months (139 patients) and at 12 months (128 patients) after ischemic or hemorrhagic strokes. Global PSF and certain PSF domains (physical, mental, motivational, activity-related) were measured by multidimensional fatigue inventory-20 scale. In univariate logistic regression analysis most of the studied variables (gender, marital status, education level, apathetic impairments, excessive daytime sleepiness, waist circumference, arterial hypertension, ischemic heart disease, atrial fibrillation, diabetes mellitus) were not significantly associated with global PSF as well as with any PSF aspect at 6, 9 and 12 months after stroke occurrence. On the other hand, univariate logistic regression analysis showed reliable associations between risk of global PSF, risk of all PSF domains and anxious as well as depressive signs, reliable associations between risk of mental PSF and cognitive impairments over the second half year after stroke. Multivariate logistic regression analysis revealed that depressive signs and cognitive impairments were independent predictors of mental PSF over studied post-stroke period. Screening and early management of depressive signs, anxious signs and cognitive impairments probably may be helpful for PSF prevention over the second half year after stroke occurrence.
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