White light events as photospheric flares

We consider the possibility that white light flares are due to heating of the photosphere by a flux of energetic ions and electrons impinging on it from above. Particles with energy in the range 10 MeV to 1 BeV release most of their energy to the ambient gas at about optical depth unity in the photosphere. This increase in energy produces a temperature perturbation of several hundred degrees in the layer and results in a re-radiation of the energy with a radiative relaxation time of several seconds. The consequences of this model are applied to a study of the great flare of May 23, 1967 and to the very fast event of August 11, 1954. Large numbers of very energetic electrons or protons must be produced in the first few minutes of the primary flare event if our interpretation (or one based on synchrotron emission) is correct.After this paper had been submitted and accepted for publication we received from Dr. vestka a copy of his paper, The Phase of Particle Acceleration in the Flare Development, which was then already in proof. (It appeared in Solar Phys. 13, 471.) A number of the arguments contained in our paper, which we had previously presented in abstract form (Najita and Orrall, 1969) and in part in a dissertation (Najita, 1969), are independently discussed by Dr. vestka who was unaware of our earlier work. Although the ground covered by his and our paper touches in places we have left our paper as originally submitted and believe that this independent agreement supports the conclusions of both.     

On the Measurement of PANs by Gas Chromatography and Electron Capture Detection

A fast, automated, gas chromatographic system for the airborne measurement of PAN and a series of its homologues is described and its performance is evaluated. Response factors for PAN, PPN, APAN, PiBN, and MPAN have been determined and are discussed with regard to ECD response and to potential losses in the analytical system. Calibration methods used for these tasks are described and compared. The results from this work should help investigators who are employing the widely used GC/ECD method for the measurement of peroxyacyl nitrates to evaluate peaks of PAN homologues that cannot be calibrated for by using the reported response factors.     

Palaeobotanical evidence for warm summers in the East Siberian Arctic during the last cold stage

Plant macrofossils from the “Mamontovy Khayata” permafrost sequence (71°60′N, 129°25′E) on the Bykovsky Peninsula reflect climate and plant biodiversity in west Beringia during the last cold stage. 70 AMS and 20 conventional ¹⁴C dates suggest sediment accumulation between about 60,000 and 7500 ¹⁴C yr B.P. The plant remains prove that during the last cold-stage arctic species (Minuartia arctica, Draba spp., Kobresia myosuroides) coexisted with aquatic (Potamogeton vaginatus, Callitriche hermaphroditica), littoral (Ranunculus reptans, Rumex maritimus), meadow (Hordeum brevisubulatum, Puccinellia tenuiflora) and steppe taxa (Alyssum obovatum, Silene repens, Koeleria cristata, Linum perenne). The reconstructed vegetation composition is similar to modern vegetation mosaics in central and northeast Yakutian relict steppe areas. Thus, productive meadow and steppe communities played an important role in the Siberian Arctic vegetation during the late Pleistocene and could have served as food resource for large populations of herbivores. The floristic composition reflects an extremely continental, arid climate with winters colder and summers distinctly warmer than at present. Holocene macrofossil assemblages indicate a successive paludification possibly connected with marine transgression, increased oceanic influence and atmospheric humidity. Although some steppe taxa were still present in the early Holocene, they disappeared completely before 2900 ¹⁴C yr B.P.     

Cr spinel and chromite as petrogenetic indicators in ordinary chondrites: Equilibration temperatures of petrologic types 3.7 to 6

Abstract— Many Equilibrated Ordinary Chondrites Contain (Besides Chromites Of Constant Composition) Cr Spinel With A Large Spread In Cr/(Cr + Al) Ratios. They Occur Mainly As Large Grains In Chondrules Rich In Mesostasis, Preventing Complete Equilibration In Cr/Al But Not In Fe/Mg. This Partially Equilibrated Cr Spinel Turned Out To Be Particularly Useful For The Selection Of An Appropriate Olivine/Spinel Thermometer And For The Determination Of Equilibration Temperatures. The Main Results Are:

• 1) The H3.7 To 3.8 And The L3.7 To 3.8 Chondrites Analyzed Show Temperatures Of 625 To 680 °C;
• 2) Equilibrated Chondrites Show A Range Of Olivine/Cr‐Spinel Temperatures Between 700 And 820 °C, And The Same Average Temperatures For Type 4 To 6 (Number Of Analyzed Meteorites In Brackets): H4 (9) 766 °C, H5 (7) 774 °C, H6 (3) 775 °C, L4 (5) 752 °C, L5 (4) 754 °C, L6 (1) 754 °C. These Temperatures Are Interpreted As Equilibration Temperatures. One Indication Is That The Measured Isotherms Are Straight Lines Down To Low Cr/(Cr + Al) Ratios, Which Have A Higher Fe/Mg Interdiffusion Coefficient Than Grains With High Ratios. And There Is No Correlation Of Measured Temperature With Grain Size Of Cr Spinel.
• 3) Chromites Sensu Stricto Show Temperatures About 50 To 100 °C Lower Than Cr Spinel, And A Correlation With Grain Size. This Is A Closure Temperature Established During Cooling And In Situ Crystallization.

These Results Can Best Be Interpreted By A “Rubble Pile” Model Of Parent Body Evolution. This Model Cannot Explain, However, The Absence Of Type 4 To 6 Chondrites With Temperatures As Low As For Type 3.7 To 3.8.