The Kepler mission has released \sim 4229 transiting planet candidates .
There are approximately 222 candidate systems with three planets .
Among them , the period ratios of planet pairs near 1.5 and 2.0 reveal that two peaks exist for which the proportions of the candidate systems are \sim 7.0 % and 18.0 % , respectively .
In this work , we study the formation of mean motion resonance ( MMR ) systems , particularly for the planetary configurations near 3:2 and 2:1 MMRs , and we concentrate on the interplay between the resonant configuration and the combination of stellar accretion rate , stellar magnetic field , speed of migration and additional planets .
We perform more than 1000 runs by assuming a system with a solar-like star and three surrounding planets .
From the statistical results , we find that under the formation scenario , the proportions near 1.5 and 2.0 can reach 14.5 % and 26.0 % , respectively .
In addition , \dot { M } = 0.1 \times 10 ^ { -8 } ~ { } M _ { \odot } ~ { } { yr ^ { -1 } } is propitious toward the formation of 3:2 resonance , whereas \dot { M } = 2 \times 10 ^ { -8 } ~ { } M _ { \odot } ~ { } { yr ^ { -1 } } contributes to the formation of 2:1 resonance .
The speed-reduction factor of type I migration f _ { 1 } \geq 0.3 facilitates 3:2 MMRs , whereas f _ { 1 } \geq 0.1 facilitates 2:1 MMRs .
If additional planets are present in orbits within the innermost or beyond the outermost planet in a three-planet system , 3:2:1 MMRs can be formed , but the original systems trapped in 4:2:1 MMRs are not affected by the supposed planets .
In summary , we conclude that this formation scenario will provide a likely explanation for Kepler candidates involved in 2:1 and 3:2 MMRs .