2 nd Joint SERENA-Hermean Environment Working Group Mykonos, Greece, 8-11 June, 2009 page 1 Extreme...

2ndJoint SERENA-Hermean Environment Working Group Mykonos, Greece, 8-11 June, 2009 page 1

Extreme events at Mars Lessons for Mercury

S. McKenna-Lawlor1, D. Heynderickx2, P. Nieminen3, G. Santin3, P. Concalves4, Ana Keating4, P. Truscott5, F. Lei5, R. Frahm6, D. Winningham6, D. Kirchner7, S. Barabash8, Y. Futaana8 , K. Kecskemety9, Ghee Fry10and M. Dryer11

1 Space Technology Ireland, National University of Ireland, Maynooth, Co. Kildare, Ireland2 D-H Consultancy BVBA, Dietsestraat 133/3 B-3000, Leuven, Belgium3 Space Systems Environment Analysis Section, ESA/ESTEC Noordwijk, The Netherlands4 Laboratório de Instrumentação e Física Experimental de Partículas (LIP), Av. Elias Garcia 14 - 1°, 1000-149 Lisboa, Portugal. 5 QinetiQ Aerospace Division, Farnborough, Hampshire GU14OLX, United Kingdom.6 Southwest Research Institute, San Antonio TX 7228-0510, USA7 Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, 2242, USA. 8 Swedish Institute of Space Physics, Box 812, S-98 128, Kiruna, Sweden.9 KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary10 Exploration Physics International Inc., Milford, New Hampshire 03055 USA11 NOAA Space Environment Centre, Boulder, Colorado 80305, USA.

Ongoing international efforts to develop the technologies required to send manned missions to Mars warrant that consideration be given to determining how energetic particle radiation effects this planet. The energetic particles incident at Mars have their sources in Galactic Cosmic Radiation (GCR) and in Solar Energetic Particle events (SEPs) produced in association with solar flaring.


GCR radiation consists of atomic nuclei that have been ionized and accelerated to very high energies, probably by supernova related shocks. Their composition is of the order of 85% protons and 14% alpha particles. The remaining particles are made up of heavier nuclei in the general range from lithium to uranium. Nuclides up to and including iron can be important in producing biological damage. Although the energies of cosmic ray particles can reach 1020 eV, most of the biological damage is associated with nuclei in the energy range from several hundred MeV/nucleon to a few GeV/nucleon

Galactic Cosmic Radiation (GCR)


GCR radiation varies as a function of the level of solar activity. At solar maximum enhanced numbers of particles and complex interplanetary magnetic fields present in the near Martian environment interact with incoming GCRs of relatively low energies and, thereby, remove some of the impinging particles. In consequence the GCR component present in the inner environment of Mars has a higher average energy but a lower fluence at solar maximum than is the case at solar minimum. Seasonal atmospheric changes also contribute to differences between the plots.

Galactic Cosmic Radiation (GCR)


GCR fluxes for 17/04/2002 and 05/12/2006


Significant solar flares may be associated with the acceleration of particles to high energies.

Solar Energetic Particle events (SEPs) associated with Impulsive Flares which are of rather short duration and feature a high proportion of protons, originate in flare-site accelerated particles. They do not pose a significant radiation hazard and will be no longer considered here.

Gradual SEP Events are of longer duration (days) and accelerated in fast, CME-driven shocks. They typically show a rapid (tens of minutes to an hour), rise in proton fluxes followed in some cases by a second, occasionally higher, intensity peak when the shock arrives at the observer. The particle profile recorded depends on where the observer is located relative to the moving shock source.

Solar Energetic Particle (SEP) events


Most SEP events feature enhanced fluxes of protons with energies < 100 MeV and, although the incident fluxes of these particle fluxes can be high, their energies are low relative to those of GCRs. However, the arrival at Mars of fluxes of flare associated protons with energies > 10 MeV pose a hazard to personnel engaged in extravehicular activity while solar protons with energies > 30 MeV are a threat to those located in thinly shielded habitats.



Although SEPs are more likely to occur during the five years corresponding to the energetic particle events occurring around solar maximum (Feynman, 1993, 2002) such events are at present unpredictable with regard to their times of occurrence and it should not be assumed that SEPs will not occur under solar minimum conditions.



Due to the fact that the relative positions of the Sun, Earth and Mars are constantly changing, while also Coronal Mass Ejections (CMEs) are often strongly directional, it can be the case that some energetic particle events recorded at the Earth do not arrive at Mars. In other geometries energetic particles that impact Mars may not be recorded at Earth.



The Present Study

Two complementary intervals when significant proton related flare events occurred close to the minimum and the maximum phases of Solar Cycle 23, were selected for study.

The enhanced proton radiation levels were recorded on these occasions aboard the Mars Express spacecraft (Solar Minimum/ December 2006) and aboard the Nozomi and Mars Odyssey spacecraft (Solar Maximum/ April 2002).

The role that the impinging particles played on these occasions (taking into account the pertaining background galactic cosmic ray radiation), in producing energetic particle radiation (expressed as Effective Dose) at the Viking-1 and Phoenix landing sites at Mars was determined using the Mars Energetic Radiation Environment Model (MarsREM) recently developed at ESA/ESTEC.


Records of energetic particle radiation made at Mars are characteristically incomplete due to gaps in data taking due to operational constraints.

The particle events recorded at Mars considered in the present study were selected to correspond with occasions when comprehensive particle signatures were measured at related times aboard spacecraft in the close Earth environment

The Hakamada-Akasofu-Fry version 2 (HAFv.2) predictive model can potentially be utilized to demonstrate that the traveling shocks/energetic particles recorded at Earth went on to produce the particle signatures recorded at Mars.

The Present Study


In the cases of the events of December, 2006, complementarity was established between events recorded close to the Earth and in the near Mars environment. Thus, the comprehensive particle events recorded close to the Earth could be used as proxies for the particle radiation that arrived at Mars, arbitrarily assuming that the particle intensity fell off as 1/r2 (where r is the pertaining helio-radial distance).

This scaling is a debatable one since recommendations for scaling vary in the literature between R-2 and R-3.3 (e.g. Reames and Ng, 1998, Smart and Shea, 2003).

The Present Study


SEP events in December 2006

NOAA Active Region 0930, transited the solar east limb on December 5, 2006 at S06º and produced over the following 9 days four X-class flares each accompanied by a metric Type II burst This activity occurred at the start of the minimum phase of Solar Cycle 23

X9.0 (December 5, 10:34UT)X6.5 (December 6, 18:42 UT)X3.4 (December 13, 02:24 UT)X1.5 (December 14, 22:10 UT)


Terminology

In the terminology of predictive modeling, the performance of a model in predicting shock arrivals is expressed in the following terms:

HIT: Shock predicted and observed to arrive at a particular heliospheric location within ±24h of its observed detection time.

MISS: Shock detected at a particular heliospheric location but predicted to arrive at a time more than 24h before or after this detection, or predicted not to arrive at all.

FALSE ALARM: Shock predicted to arrive, but not detected, within a window of 1-5 days (Earth) following a particular solar event.

CORRECT NULL: Shock neither predicted nor detected at a particular heliospheric location within a window of 1-5 days (Earth) following a particular solar event.


Predictions of HAFv.2 vs measurements (December, 2006)

The HAFv.2 model indicated that disturbances associated with the X 9 and the X 6.5 flares on 5 and 6 December interacted with each other to produce a composite shock which was predicted to arrive at L1 on 8 December at 07.00 UT. A shock was indeed recorded at ACE in MAG data on 8 December at 04.11 UT (3 hours early) i.e. well within the period of ± 24 hours considered to constitute a “HIT” when making such predictions. Table 1 shows that the arrivals of all of the shocks emanating from the four flares of December 2006 arrived well in accordance with their predicted values (all HITS).

Shock Predicted Arrival Measured Arrival ΔT Category 1-2 07.00 UT (08 Dec) 04.11 UT (8 Dec) - 2h49m HIT3 14.00 UT (14 Dec) 13.52 UT(14 Dec) - 8m HIT4 12.00 UT (16 Dec) 17.21 UT(16Dec) +5h21m HIT


Particles / shocks at Venus (December, 2006)

Background counts in the ELS and IMA data recorded aboard Mars Express MEX on 5 December (after a data gap) indicated that energetic particle radiation arrived at the spacecraft at < 05.30 UT.

HAFv.2 predicted the arrival at Venus at ~04.00 UT on 8 December of a composite shock associated with the flares of 5 and 6 December. An ESP event at 09.00 UT on 7 December indicated the arrival of this shock, 19h early (HIT)


Particles / shocks at Mars (December, 2006)Energetic particles were present in the background counts of MEX/ELS from < 05.30 UT (after a data gap)

HAFv.2 predicted that the eastern flank of shock 1-2 would decay to an MHD wave after passing Venus and no shock signature was expected or seen in the MEX data (correct null/cn) It is possible that a shock passed during data gaps and was missed.


HAFv.2 predicted the arrival of a shock at Mars at ~ 00.00 UT on 20 December 2006 in association with interacting shocks emanating from the flares of 13 and 14 December, 2005.

A shock signature was found in the data of ASPERA-3 close to the predicted time (HIT).


Energetic particle events at Earth April 2002 (Solar Maximum)

NOAA Region 9906 was characterized by the production of many CMEs during its disk passage in April, 2002.

An LDE (Long Duration Event) flare (Class X1.5/1F), took place at S24,W84 in this region. The start of the flare was recorded aboard GOES-9 in soft X-rays at 00.43UT. An accompanying metric Type II radio burst was recorded at three ground stations. It was estimated based on these observations that Vshock = 3D 760 km/s.

A partial halo was recorded in SOHO/LASCO data at 01.51 UT on 21 April with a plane of sky speed of 2427 km/s at position angle 273°. This ejection was first seen as a bright front over the west limb. By 02.26 UT, although it was very faint along its eastern front, it was seen to be a full halo event.


It is speculated that the speed of the leading edge of the event might have been the speed of the shock itself. In such a case, the metric Type II emissions would be from the slower portion of the shock along its eastern flanks.

Based on this scenario, the HAFv.2 model predicted that the shock would arrive at Earth at 04.10 UT on 23 April and a shock indeed arrived that was recorded aboard SOHO and ACE at 02.07 UT (HIT)

Energetic particle events at Earth April 2002 (Solar Maximum)


The graphics show the modeled cross section of the 4-pi ICME shock modified by oncoming stream-stream interactions


ACE - NOZOMI measurements (April 2002)

Intensity-time profilesfrom April 20, 2002 to April 25, 2002. The dashed line represents a Halo CME with an onset at 01.51UT on April 21, 2002. The ACE/ULEIS proton time profile is also shown as well as NOZOMI p and e profiles.



The Solar Proton Monitor (SPM) record obtained aboard Nozomi in the range 30 keV - 1 MeV. shows that the instrument was saturated for about six hours on 23 April.2002.On 25 April a problem was found with part of the communication and altitude control system of the spacecraft while also a short mode failure occurred in one of the power circuits. The telemetry and the main thruster never recovered.

SOHO and ACE observed the active region on the west limb of the Sun as seen from the Earth, magnetic connectivity was good and a very rapid rise in particle flux was recorded both in protons > 10 MeV and in higher energy particles. A related shock arrived on 23 April

The Nozomi spacecraft at 1.3 AU had a longitudinal angle of 900 with ACE The flare location seen from Nozomi was E06.. A shock arrived at the spacecraft on 22 April and there was a rapid rise in particle fluxes.

Mars Odyssey was in an unfavourable location to receive particles as it was far behind the East limb of the Sun.

It was noted by the observers that approximately three days was required for the onboard MARIE energetic particle instrument to reach peak flux.


The figure shows uncorrected 5 minute differential proton fluxes The data used were taken from http://goes.ngdc.noaa.gov/data/avg/2006/G1150612.TXT

GOES-11 data (December 2006 – Solar minimum)

GOES-08 data (April 2002 – Solar maximum)


The crosses in the spectrum plot represent the fluences for each GOES channel. Both spectra are fitted by an exponential function f = Aexp (-be) Left A= 4.444. b= 0.0644right A = 4.023 b = 0.667. The solid line is the part of the spectrum that was input to the MarsREM models.

GOES-11 data (December 2006 – Solar minimum)

GOES-08 data (April 2002 – Solar maximum)


MarsREM effective doses

Viking 1 (22.5N, 48.0W)

Apr 2002 Dec 2006

GCR H /4.31 103 1.15 104 / 7.50 103

GCR He /7.59 102 8.60/1.15 103

GCR Li 3.39 101

GCR Fe

SEP 1.67/2.76 102 /3.93 102

The spectra measured at Earth during December, 2006 and April 2002 were inserted into the Mars Energetic Radiation Environment (MarsREM) model to estimate the effective doses in μSv pertaining at the Viking 1 landing site due to the combined precipitation of flare related particle radiation and background cosmic ray radiation.




Viking 1 (22.5N, 48.0W) Phoenix (68.5N, 125.8W)

Apr 2002 Dec 2006 Apr 2002 Dec 2006

GCR H

5.98/4.31 103 1.15 104 / 7.50 103

5.78/4.31 103

GCR He

5.04 103 / 7.59 102

8.60/1.15 103 / 4.11 103

GCR Li

2.20 101 3.39 101

GCR Fe

6.78 101 9.04 101

SEP 1.67/2.76 102 3.32/3.93 102 2.25/2.62 102

/ 3.67 102

Total 1.13 104 / 5.35 103

2.06 104 / 9.04 103

/ 8.68 103

Table 1. MarsREM effective doses (μSv) for different landing sites and two SEP event periods. GCR dose rates were multiplied by the durations of the respective events. dMEREM/eMEREM doses are presented where available.



For emerem we should use water ice / dry composition and then discuss the difference observed in the resultsFor dMEREM we can try the following user defined composition (andesite composition + 50% water)> > H2O = 50.00%> SiO2 = 26.95%> Fe2O3= 4.30%> Al2O3 = 5.39 %> MgO = 2.13 %> CaO = 2.97 %> Na2O = 3.28 %> K2O = 4.98 %> with a density of 1.228 g/cm3.> ( the water density was reduced to 1/1.09 because it should be ice and a > porosity of 20 % was used for the soil).

Two complementary intervals when significant flare related protons were recorded in situ at Mars during the minimum and maximum phases of Solar Cycle 23 were studied. These records were incomplete due to operational constraints.

The HAFv.2 model was used to verify that the particle events recorded at Mars were in each case associated with comprehensive particle records recorded close to Earth. The latter fluxes were then used (with a scaling factor) as proxies to determine the overall fluxes arriving at Mars.

The effective dose at the Viking 1 landing site was then calculated for both events using the MarsREM model while taking into account relevant GCR radiation.

These doses were compared with those correspondingly present at the Phoenix landing site. A factor to emerge from the data may be the influence of sputtered particles on the dose.

Conclusion


The influence of the Hermean terrain in producing sputtered particles will provide important insights into local topography.

The influence of the galactic cosmic ray background at different times in the solar cycle should be taken into account.

Lessons for Mercury

2 nd Joint SERENA-Hermean Environment Working Group Mykonos, Greece, 8-11 June, 2009 page 1 Extreme...

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