52 research outputs found
Parametric Forcing of Waves with Non-Monotonic Dispersion Relation: Domain Structures in Ferrofluids?
Surface waves on ferrofluids exposed to a dc-magnetic field exhibit a
non-monotonic dispersion relation. The effect of a parametric driving on such
waves is studied within suitable coupled Ginzburg-Landau equations. Due to the
non-monotonicity the neutral curve for the excitation of standing waves can
have up to three minima. The stability of the waves with respect to long-wave
perturbations is determined a phase-diffusion equation. It shows that the
band of stable wave numbers can split up into two or three sub-bands. The
resulting competition between the wave numbers corresponding to the respective
sub-bands leads quite naturally to patterns consisting of multiple domains of
standing waves which differ in their wave number. The coarsening dynamics of
such domain structures is addressed.Comment: 23 pages, 6 postscript figures, composed using RevTeX. Submitted to
PR
Christian-Muslim Relations in a State Church Situation: Politics of Religion and Interfaith Dialogue
No abstract availabl
Mars Science Laboratory relative humidity observations : Initial results
The authors would like to express their gratitude to the MSL and REMS instrument teams in making this wonderful Mars mission come true. AriâMatti Harri and Hannu Savijarvi are thankful for the Finnish Academy grants 132825 and 131723.Peer reviewedPublisher PD
Secular Climate Change on Mars: An Update Using MSL Pressure Data
The South Polar Residual Cap (SPRC) on Mars is an icy reservoir of CO2. If all the CO2 trapped in the SPRC were released to the atmosphere the mean annual global surface pressure would rise by approx. 20 Pa. Repeated MOC and HiRISE imaging of scarp retreat rates within the SPRC have led to the suggestion that the SPRC is losing mass. Estimates for the loss rate vary between 0.5 Pa per Mars Deacde to 13 Pa per Mars Decade. Assuming 80% of this loss goes directly to the atmosphere, and that the loss is monotonic, the global annual mean surface pressure should have increased between approx. 1-20 Pa since the Viking mission (19 Mars years ago)
Mars Science Laboratory Observations of the 2018/Mars Year 34 Global Dust Storm
Mars Science Laboratory Curiosity rover observations of the 2018/Mars year 34 global/planet-encircling dust storm represent the first in situ measurements of a global dust storm with dedicated meteorological sensors since the Viking Landers. The Mars Science Laboratory team planned and executed a science campaign lasting approximately 100 Martian sols to study the storm involving an enhanced cadence of environmental monitoring using the rover's meteorological sensors, cameras, and spectrometers. Mast Camera 880-nanometer optical depth reached 8.5, and Rover Environmental Monitoring Station measurements indicated a 97 percent reduction in incident total ultraviolet solar radiation at the surface, 30 degrees Kelvin reduction in diurnal range of air temperature, and an increase in the semidiurnal pressure tide amplitude to 40 pascals. No active dust-lifting sites were detected within Gale Crater, and global and local atmospheric dynamics were drastically altered during the storm. This work presents an overview of the mission's storm observations and initial results
Mars Science Laboratory Observations of the 2018/Mars Year 34 Global Dust Storm
Mars Science Laboratory Curiosity rover observations of the 2018/Mars year 34 global/planetĂą encircling dust storm represent the first in situ measurements of a global dust storm with dedicated meteorological sensors since the Viking Landers. The Mars Science Laboratory team planned and executed a science campaign lasting approximately 100 Martian sols to study the storm involving an enhanced cadence of environmental monitoring using the roverâs meteorological sensors, cameras, and spectrometers. Mast Camera 880Ăą nm optical depth reached 8.5, and Rover Environmental Monitoring Station measurements indicated a 97% reduction in incident total ultraviolet solar radiation at the surface, 30K reduction in diurnal range of air temperature, and an increase in the semidiurnal pressure tide amplitude to 40ĂÂ Pa. No active dustĂą lifting sites were detected within Gale Crater, and global and local atmospheric dynamics were drastically altered during the storm. This work presents an overview of the missionâs storm observations and initial results.Plain Language SummaryThe 2018 Mars global dust storm was observed by six spacecraft in orbit and two rovers on the surface. This paper provides an overview and description of the Mars Science Laboratory Curiosity roverâs observations during the storm. For approximately 100 Martian days (sols), the rover conducted an enhanced cadence of environmental observations to study the storm. These are the first observations of a Martian global dust storm with meteorological sensors near the equator. Atmospheric opacity reached a peak of 8.5, attenuating ~97% of the total solar ultraviolet radiation at the surface. Most of the dust was sourced from outside Gale Crater, with no indications of dust lifting within the crater during the height of the storm. Meteorological conditions were substantially altered, with changes to the pressure, temperature, and humidity patterns. Dust devil activity ceased for several weeks due to the reduction in temperature contrast between the surface and atmosphere. There was no indication of unusual aeolian transport, suggesting Martian global dust storms are not a major cause of sand dune movement.Key PointsThe Curiosity rover conducted a dedicated science campaign to study the 2018 Mars global dust stormAtmospheric opacity reached a peak of 8.5, and horizontal visibility dropped to 2.7ĂÂ kmMeteorological conditions in Gale Crater were substantially altered, with changes to the pressure, temperature, and humidity cyclesPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147828/1/grl58365_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147828/2/grl58365.pd
Calibration and first results of relative humidity sensor MEDA HS onboard M2020 rover
MEDA HS is the relative humidity sensor on the Mars 2020 Perseverance rover provided by theFinnish Meteorological Institute (FMI). The sensor is a part of Mars Environmental DynamicAnalyzer (MEDA), a suite of environmental sensors provided by Centro de AstrobiologĂa in Madrid,Spain. MEDA HS, along with METEO-H in ExoMars 2022 surface platform, is a successor of REMS-Hon board Curiosity.Calibration of relative humidity (RH) instruments for Mars missions is challenging due to the rangeof RH (from 0 to close to 100%) and temperature conditions (from about -90 ÂșC to + 22 ÂșC) thatneed to be simulated in the lab. Thermal gradients in different parts of the system need to be wellknown and controlled to ensure reliable reference RH readings. For MEDA HS the calibration testshave been performed for different models of MEDA HS in three Martian humidity simulatorlaboratories: FMI laboratory, Michigan Mars Environmental Chamber (MMEC) and DLR PASLAB(Planetary Analog Simulation Laboratory). MEDA HS flight model was tested at FMI together with flight spare and ground reference models inlow pressure dry CO2 gas from +22ÂșC to -70ÂșC and in saturation conditions from -40ÂșC down to-70ÂșC. Further, the MEDA HS flight model final calibration is complemented by calibration datatransferred from an identical ground reference model which has gone through rigorous testingalso after the flight model delivery. During the test campaign at DLR PASLAB that started inAutumn 2020, MEDA HS has been calibrated over the full relative humidity scale between -70 to-40ÂșC in CO2 in the pressure ranges from 5.5 to 9.5 hPa, representative of Martian surfaceatmospheric pressure. The results can be extrapolated to higher and lower temperatures.In this presentation the final flight calibration and performance of the MEDA HS will be presentedtogether with first results expected from the surface of Mars by the Perseverance rover
Pressure observations by the curiosity rover : Initial results
The authors would like to express their gratitude to the MSL and REMS instrument teams in making this wonderful Mars mission come true. Ari-Matti Harri and Hannu Savijarvi are thankful for the Finnish Academy grants 132825 and 131723.Peer reviewedPublisher PD
Secular Climate Change on Mars: An Update Using One Mars Year of MSL Pressure Data
The South Polar Residual Cap (SPRC) on Mars is an icy reservoir of CO2. If all the CO2 trapped in the SPRC were released to the atmosphere the mean annual global surface pressure would rise by approximately 20 Pa. Repeated MOC and HiRISE imaging of scarp retreat within the SPRC led to suggestions that the SPRC is losing mass. Estimates for the loss rate vary between 0. 5 Pa per Mars Decade to 13 Pa per Mars Decade. Assuming 80% of this loss goes directly into the atmosphere, an estimate based on some modeling (Haberle and Kahre, 2010), and that the loss is monotonic, the global annual mean surface pressure should have increased between approximately 1-20 Pa since the Viking mission (approximately 20 Mars years ago). Surface pressure measurements by the Phoenix Lander only 2.5 Mars years ago were found to be consistent with these loss rates. Last year at this meeting we compared surface pressure data from the MSL mission through sol 360 with that from Viking Lander 2 (VL-2) for the same period to determine if the trend continues. The results were ambiguous. This year we have a full Mars year of MSL data to work with. Using the Ames GCM to compensate for dynamics and environmental differences, our analysis suggests that the mean annual pressure has decreased by approximately 8 Pa since Viking. This result implies that the SPRC has gained (not lost) mass since Viking. However, the estimated uncertainties in our analysis are easily at the 10 Pa level and possibly higher. Chief among these are the hydrostatic adjustment of surface pressure from grid point elevations to actual elevations and the simulated regional environmental conditions at the lander sites. For these reasons, the most reasonable conclusion is that there is no significant difference in the size of the atmosphere between now and Viking. This implies, but does not demand, that the mass of the SPRC has not changed since Viking. Of course, year-to-year variations are possible as implied by the Phoenix data. Given that there has been no unusual behavior in the climate system as observed by a variety of spacecraft at Mars since Phoenix, its seems more likely that the Phoenix data simply did not have a long enough record to accurately determine annual mean pressure changes as Haberle and Kahre (2010) cautioned. In the absence of a strong signal in the MSL data, we conclude that if the SPRC is loosing mass it is not going into the atmosphere reservoir
Dust Devil Frequency of Occurrence and Radiative Effects at Jezero Crater, Mars, as Measured by MEDA Radiation and Dust Sensor (RDS)
The Mars Environmental Dynamics Analyzer, onboard the Perseverance rover, is a
meteorological station that is operating on Mars and includes, among other sensors, the radiometer Radiation
and Dust Sensor (RDS). From RDS irradiance observations, a total of 374 dust devils (DDs) were detected
for the first 365 sols of the mission (Ls = 6°â182°), which along with wind and pressure measurements,
we estimated a DD frequency of formation at Jezero between 1.3 and 3.4 DD km â2 sol â1 (increasing as we
move from spring into summer). This frequency is found to be smaller than that estimated at the Spirit or
Pathfinder landing sites but much greater than that derived at InSight landing site. The maximum in DD
frequency occurs between 12:00 and 13:00 local true solar time, which is when the convective heat flux and
lower planetary boundary layer IR heating are both predicted to peak in Jezero crater. DD diameter, minimum
height, and trajectory were studied showing (a) an average diameter of 29 m (or a median of 25 m) and a
maximum and minimum diameter of 132 ± 63.4 and 5.6 ± 5.5 m; (b) an average minimum DD height of 231 m
and a maximum minimum-height of 872 m; and (c) the DD migration direction is in agreement with wind
measurements. For all the cases, DDs decreased the UV irradiance, while at visible or near-IR wavelengths both
increases and decreases were observed. Contrary to the frequency of formation, these results indicate similar
DD characteristics in average for the studied period
- âŠ